Yes, during fasting you can have plain water, black coffee, and unsweetened tea; any drink with calories breaks the fast.
Thirst hits long before hunger, so drinks matter during a fasting window. The short rule many follow: zero calories keep the fast intact, calories end it. That simple line still leaves plenty of gray areas—sparkling water, lemon slices, sweeteners, broth, diet soda, and pre-workout mixes. This guide explains what fits a fast, where people slip, and how medical or religious fasts change the rules.
Drinking During A Fast: What’s Allowed
Most time-restricted plans allow water, black coffee, and plain tea. These options carry no meaningful calories and don’t nudge insulin. On stricter styles—water-only days or multi-day stints—many people limit drinks to water plus electrolytes. Medical or religious fasts can set different boundaries. For surgery prep and certain lab tests, rules are set by your care team, not by a diet book.
Fast-Safe Drinks, Gray Areas, And Clear No-Gos
Use the table below as a quick checkpoint. It keeps things simple: what the drink is, how many calories show up in a typical serving, and whether it usually fits a fasting window.
| Drink | Typical Calories | Fit For A Fast |
|---|---|---|
| Plain Water (Still Or Sparkling) | 0 | Allowed |
| Black Coffee (No Add-Ins) | ~2 per cup | Allowed |
| Plain Tea (Green, Black, Herbal) | 0–2 per cup | Allowed |
| Electrolyte Tablets (Sugar-Free) | 0–5 | Allowed In Short Amounts |
| Diet Soda / Zero Sugar Drinks | 0 | Depends On Tolerance |
| Lemon Slice In Water | < 2 | Usually Fine |
| Bone Broth | 30–50 per cup | Avoid During Strict Windows |
| Milk, Cream, Sugar, Honey | Varies (20–100+) | Avoid |
| Protein Shakes, BCAAs With Sweeteners | Varies (0–150+) | Avoid |
| Alcohol | 70+ per serving | Avoid |
Why “Zero” Calories Keeps The Window Clean
Time-based plans work by creating long gaps without energy intake. Water, plain tea, and coffee add fluid without energy. That lets appetite ease off and helps some people maintain a plan day after day. Large reviews from academic groups report that time-based eating can match standard calorie cutting for weight loss when people stick with it, which is why drink choices that don’t add energy matter during the fasting stretch. See an overview from Harvard Health Publishing.
Black Coffee: Benefits, Limits, And Tolerance
One or two cups of black coffee fit most windows. Coffee’s trace calories are too low to change the energy gap in a meaningful way. Some people feel better with a small cup early in the window, others skip it due to jitters or reflux. If you add cream, milk, sugar, or flavored syrup, the window ends. A good middle path for people who like flavor: brew stronger and add extra water to thin the taste without adding energy.
Tea During A Fast
Unsweetened green, black, oolong, white, or plain herbal blends are fine. Avoid sweetened bottled tea. Avoid latte blends with milk. Strong mint or ginger can calm a grumbling stomach for some drinkers. The goal is comfort without energy intake.
What About Diet Soda And Sweeteners?
Calorie-free sodas and mixes don’t add energy, so many people keep them in. A small group feels hungrier after sweet tastes even when calories read zero. If cravings spike or you notice rebound eating, swap those drinks for plain water or tea during the window. If the drinks help you stick to the plan without rebound, keep them in light amounts.
Types Of Fasts And Beverage Rules
Not every fast is the same. Here’s how drink rules shift across common use cases. This section also flags times when a care team sets the rules—your schedule must match those directions even if a diet blog says otherwise.
Time-Restricted Eating (Daily Windows)
Common shapes include 16:8 or 14:10, where the first number is hours without energy and the second is the eating window. During the gap, stick to water, black coffee, and unsweetened tea. Many people add a sugar-free electrolyte tab during hot weather or long workouts. That’s fine so long as the tab is truly zero-calorie.
Alternate-Day Or 5:2 Style
Some plans set near-zero days or very low-energy days. On a near-zero day, use the same drink rules as a daily window. On low-energy days, a broth or a small milk splash may fit if the plan allows a set energy target, but the window isn’t strict in that case. Keep labels close; small slips add up on a tight budget.
Water-Only Stints (24–72 Hours)
These periods are stricter. Stick to water. Add plain sodium/potassium electrolytes if your clinician advised it. Skip coffee and tea if you’re prone to palpitations or reflux without food. Multi-day stints aren’t for everyone; medical guidance matters for people on medication, with a history of disordered eating, or with chronic conditions.
Religious Fasts
Rules vary by tradition and by event. Some practices forbid both food and drink during daylight hours. Others allow water. Follow your faith’s guidance and local leadership. If you have a medical need, speak with both your clinician and your faith leader about allowances outside the set hours.
Medical Fasts: Surgery Prep And Lab Work
Pre-procedure rules are not diet choices; they manage safety. For many elective procedures, updated anesthesia guidance allows clear liquids up to two hours before anesthesia for healthy adults, with a stricter cutoff for solids. Always follow the written plan you received. For lab work, policies vary by test; water is usually allowed, while coffee, tea, and gum often lead to rescheduling. You can read the anesthesia guidance from the American Society of Anesthesiologists and a practical lab-fasting explainer from the Cleveland Clinic.
What Drinks Are Okay During A Fasting Window?
Here’s a field guide to common drinks with quick tips for how to use each one without tripping your plan.
Water: Still, Sparkling, Or Mineral
Water is the core option. Mineral or sparkling water adds variety without energy. If you crave flavor, a wedge of lemon or cucumber keeps it fresh. Keep the wedge small to avoid juice.
Coffee: Black And Simple
Grind fresh, brew strong, and skip add-ins. If bitterness is an issue, dilute with hot water. Set a daily cap if sleep or palpitations pop up. Many people feel steady with one cup early and a second cup near midday.
Tea: Green, Black, Or Herbal
Tea offers a wide range of flavors with a gentle lift. Choose loose-leaf or simple bags without dried fruit. Rooibos, peppermint, or ginger work well late in the window since they’re caffeine-free.
Electrolytes: When Heat Or Training Enters
Choose a tab with zero calories and no sugar alcohol load that upsets your stomach. Use during long sessions, hot weather, or headaches linked to low sodium. If you notice swelling or high blood pressure, ask your clinician about sodium limits before using these regularly.
Zero-Sugar Sodas And Flavored Waters
These can help with cravings. If they spark hunger or trigger a snack run, move them to your eating window and lean on tea or sparkling water during the gap.
Broth, Cream, Milk, And “Bulletproof” Drinks
These add energy and end a strict window. They can be used inside the eating window as a bridge to a full meal, but they don’t fit the fasting stretch.
Side Effects Linked To Drinks During Fasts
Most people feel fine with water, tea, and coffee. A few run into issues tied to timing, caffeine, or hydration. Use the checklist below to solve common snags.
Headaches Or Dizziness
Drink water early and often. Add a zero-calorie electrolyte tab if you sweat a lot or if your meals are very low in sodium. Skip large caffeine doses on an empty stomach; sip slowly instead.
Reflux Or Stomach Discomfort
Pick mild tea over dark roast coffee. Try smaller sips. Save acidic drinks—vinegar shots, citrus infusions—for the eating window. If you take reflux medicine, ask your clinician about timing on fast days.
Jitters And Sleep Disruption
Cap coffee at one or two cups and stop early in the day. Swap late drinks for herbal tea. If you still feel wired, cut back caffeine across the week.
Hydration Targets During Fasting Windows
There’s no single target that fits everyone. A simple plan: drink to thirst, then add a little more during heat, workouts, or long windows. Urine that’s pale straw usually signals adequate hydration. If you’re prone to kidney stones, your clinician may set a higher intake; follow that plan.
Workout Days
Short morning sessions often feel fine with just water. For longer or sweaty sessions, add a zero-calorie electrolyte tab. If you need energy for intense training, shift the workout toward your eating window or bring a small carbohydrate source for use just before the session begins so you aren’t breaking a planned fasting stretch.
Special Cases You Should Plan For
These scenarios call for extra care. If a plan from a clinician conflicts with a diet rule, the clinical plan wins every time.
| Situation | Drinks Allowed | Notes |
|---|---|---|
| Pre-Surgery (Elective) | Clear liquids up to 2 hours before anesthesia, solids stop earlier | Follow the written plan from your team; safety first. |
| Blood Tests | Usually water only; some tests allow no fasting | Read your lab slip; coffee or gum can delay testing. |
| Pregnancy Or Breastfeeding | Hydration first; follow clinician guidance | Energy needs differ; fasting plans often change. |
| Diabetes Or Medications | Water, tea, coffee as cleared by your clinician | Some drugs require food; dosing plans may shift. |
| Religious Observance | Set by tradition and local leadership | If health needs arise, ask about accommodations. |
| Kidney Or Heart Conditions | Hydration plan set by your clinician | Fluid or sodium caps may apply. |
Simple Rules That Keep You On Track
1) Zero Calories During The Window
If a label lists energy, save that drink for your eating window. When there’s no label, think through the contents: fruit juice, milk, creamers, syrups, collagen, oil, and amino drinks all add energy or protein. That ends a strict stretch.
2) Black Coffee And Plain Tea Are Fine
Skip additives. If taste feels harsh, dilute or switch to a lighter roast or herbal blend. Keep caffeine in a range you handle well.
3) Watch Sweet Taste If Cravings Spike
If diet sodas or flavored powders push you toward snacks, swap them out during the fasting hours. Use sparkling water, herbal tea, or plain water instead.
4) Medical Plans Override Diet Rules
For surgery prep and some tests, windows and drink lists come from your care team. The stakes are higher than weight or habit building. Use their plan to the letter and ask questions early if anything is unclear.
A Quick One-Day Sample With Drink Timing
This outline shows how drinks can fit a common 16:8 shape. Shift times to match your day.
7:00
Wake and drink a tall glass of water. If you like, add a pinch of salt during hot months.
8:00
One cup of black coffee. If caffeine hits hard, swap for green tea.
10:30
Herbal tea or sparkling water. Short walk if hunger pops up.
12:00–20:00 (Eating Window)
Regular meals. Any flavored drinks, lattes, smoothies, or broths go here. End the day with water.
20:00–Next Day 12:00 (Fasting Window)
Water, tea, and black coffee only. Shut down caffeine mid-afternoon to protect sleep.
FAQ-Free, But Here’s A Handy Recap
— Zero-calorie drinks keep a fasting stretch intact. Water, black coffee, and unsweetened tea lead the list.
— Lemon wedges are fine. Juice, milk, cream, sugar, syrups, broth, and alcohol end the window.
— Diet sodas fit for many people, but if cravings rise, set them aside during the window.
— Surgery prep and lab work come with their own rules. Follow those directions even if a diet plan says something else.
— Build a drink routine you can repeat. Consistency beats perfection.
Why This Works Long Term
People tend to stick with plans that feel simple. Swapping energy-bearing drinks for water, tea, and coffee keeps fasting hours clear and repeatable. Reviews from leading research groups show time-based plans can help with weight control when people can live with the routine. If your plan needs medical oversight due to conditions or medications, loop your clinician in early. You’ll get tailored advice on drink timing, electrolytes, and caffeine limits that match your health record.