No, calorie-containing drinks break a fasting window; stick to water, black coffee, or unsweetened tea during a fast.
Fasting plans set a clean line: energy in, fast off. Liquids with calories add energy, trigger digestion, and end the fasting state. That said, many people still want a warm mug or some flavor while they wait for their eating window. This guide shows what actually fits during a fast, what quietly breaks it, and how to pick drinks based on your goals.
What Counts As “Drinking Calories” During A Fast
Any drink that supplies energy—sugars, protein, or fat—puts you on the “fed” side of the line. Soda, juice, milk, smoothies, and creamy coffee are clear examples. Even a small splash of cream or a scoop of collagen adds measurable energy. For time-restricted eating and alternate-day plans, the typical rule is simple: zero energy during the fasting window.
Quick Reference: Drinks, Calories, And Fast Status
The chart below lists common choices and whether they keep a standard, calorie-abstinent fast. Portion sizes refer to typical servings.
| Drink | Typical Calories | Keeps A Calorie Fast? |
|---|---|---|
| Water (still/sparkling) | 0 | Yes |
| Black coffee | 2–5 per cup | Yes* |
| Plain tea (green/black/herbal) | 0–2 per cup | Yes* |
| Electrolyte water (unsweetened) | 0 | Yes |
| Diet soda / NNS drinks | 0 | Usually** |
| Lemon water (squeeze) | ~2–3 | Usually |
| Bone broth | 30–50 per cup | No |
| Milk / creamers | 20–120+ | No |
| Bullet coffee (butter/MCT) | 100–300+ | No |
| Protein shakes / collagen | 30–200+ | No |
| Fruit juice / smoothies | 80–300+ | No |
| Alcohol | 70–200+ | No |
*Caffeine can bother some stomachs. **Non-nutritive sweeteners don’t add energy, though research on metabolic effects is mixed; see the evidence link below.
Clean Fasting Drink Rules
Most fasting schedules allow plain water, black coffee, and unsweetened tea during the fasting window (Johns Hopkins overview). If you like bubbles, pick unflavored seltzer. If you need flavor, steep tea or drop in a cinnamon stick. Skip milk, syrups, creamers, and oils until your eating window opens.
Why Zero-Energy Drinks Don’t Break A Standard Fast
Zero-energy drinks don’t deliver carbs, amino acids, or fats. Without energy coming in, the body stays in a fasting state between meals and continues drawing on stored energy. That’s the point of time-restricted eating: hold energy intake to a set window and stay hydrated the rest of the time.
Close Variant: Drinking Calories During Fasting — What Actually Breaks It
People use the word “fast” in different ways. Here’s how the common versions treat drinks:
Time-Restricted Eating (16:8, 14:10)
Zero-energy drinks are fine. Anything with measurable energy—cream, sweetened creamers, juice, broth—ends the fast. Black coffee and plain tea fit for most people.
Alternate-Day Or 5:2 Patterns
On low-energy days, some plans allow a small meal. Coffee or tea can help appetite on those days, but calorie-containing drinks still count toward the allowance.
Religious Or Medical Fasts
Rules vary. Some fasts restrict all liquids for set hours; others allow water only. If your situation is medical, defer to your clinician’s instructions.
Does Black Coffee Break A Fast?
Plain coffee has minimal energy per cup, so it doesn’t end a standard calorie-abstinent fast. Many clinical overviews place black coffee and tea in the “okay” column during fasting windows, alongside water. If coffee upsets your stomach on an empty gut, switch to tea or wait for your eating window.
What About A Splash Of Milk Or Cream?
Even small dairy adds energy and ends a stricter fast. If your plan is flexible and you only care about appetite control, you might accept a splash. If your plan is strict time-restricted eating, save it for later.
Do Diet Drinks Or Sweeteners Break A Fast?
Drinks sweetened with non-nutritive sweeteners (NNS) don’t add energy, so they don’t end a caloric fast on that basis. Human trials that pooled short-term tests report no meaningful change in acute glucose or insulin after NNS compared with water. That said, some people feel hungrier with sweet taste, and long-term effects are still under study. If hunger spikes or cravings show up, stick to plain options.
What About Lemon Water, Cinnamon, Or Vinegar?
A squeeze of lemon adds a few units of energy. For most people, that tiny amount won’t matter for a simple time-restricted schedule, but it technically ends the purest version of a fast. Cinnamon sticks or tea bags add flavor without energy. Vinegar doesn’t add energy in typical splash amounts, though it can irritate some stomachs.
Hydration And Electrolytes While You Wait To Eat
Hydration helps with headaches and low energy during a fast window. Plain water works for most people. During longer stretches, a pinch of salt in water or an unsweetened electrolyte tablet can help if you feel light-headed. Pick zero-energy products during the fast; save sweetened packets for your eating window.
Goals Change The Rule Set
Not every fast chases the same outcome. Match your drinks to the job at hand.
Goal: Weight Control
Hold the fasting line: water, plain tea, and black coffee. Sweetened drinks or dairy end the window and can raise energy intake. If you use NNS drinks, watch your own response. If cravings climb, go back to plain options.
Goal: Blood Sugar Stability
Stick with zero-energy choices. If you live with diabetes or take glucose-lowering drugs, talk to your care team before trying fasting patterns. Some people see drops in need for medicine; others need adjustments to avoid low sugar during the window.
Goal: Athletic Training
Many athletes fast overnight and train before eating. Plain water and black coffee fit that plan. For long sessions, you may need energy during the effort; that ends the fast by design.
Simple Drink Swaps For Fasting Windows
Use these easy swaps to lower energy intake while keeping flavor or routine.
Morning Routine
- Latte → Americano or black coffee.
- Sweet iced tea → Unsweetened iced tea with lemon wedge (skip the squeeze if you’re strict).
- Orange juice → Sparkling water with a cold-brew tea bag.
Afternoon Slump
- Soda → Seltzer with a twist of peel.
- Energy drink → Cold brew or hot tea.
- Milk tea → Hot herbal tea with a cinnamon stick.
When A “Dirty Fast” Appears In Guides
Some online plans allow small amounts of energy—often quoted as up to 50–100 units—during the fasting window. That can help adherence for some people, but it isn’t a strict fast, and results can differ. If you adopt that style, count those drinks toward your day’s energy, and judge by outcomes: appetite, sleep, training, and body metrics.
Evidence Corner: What Reputable Guides Say
Major medical centers describe fasting windows that permit water, tea, and black coffee while abstaining from energy. For accessible overviews and definitions of time-restricted eating, see the links below. Reviews of non-nutritive sweeteners suggest no acute spike in glucose or insulin compared with water during short-term tests, though longer-term effects are mixed.
How To Build Your Personal Rules
Pick the fasting schedule, then set drink rules you can keep for weeks. Keep it simple for the first two weeks so your body settles in. Use plain water as your base. Add coffee or tea if you like them on an empty gut. If you’re craving sweet taste, try a diet drink and see how your appetite responds. If hunger jumps, pull it back out.
Checklist For A Smooth Fasting Window
- Set the start and end time. Hold it daily.
- Pre-brew tea or coffee the night before if mornings feel rushed.
- Keep a large bottle on your desk to pace hydration.
- Carry unsweetened electrolyte tablets for long gaps between meals.
- Stack tasks during the fasting window to keep your mind busy.
Troubleshooting Common Snags
Headaches
Drink water first. If caffeine withdrawal hits, a modest cup of coffee often helps. For long stretches, add a pinch of salt to water if you feel light-headed.
Gnawing Hunger
Warm beverages help. Try hot tea or decaf. If appetite keeps building, shorten the window for a week, then lengthen again once it feels easy.
Sleep Disruption
Cut caffeine by early afternoon. Late-day coffee can push bedtime and lower sleep quality.
Goal-Based Drink Planner
Use this table to map a plan you can stick with. Adjust based on your response.
| Goal | Drink Choices During Fast | Skip Until Eating Window |
|---|---|---|
| Time-restricted eating | Water, black coffee, plain tea, unsweetened seltzer | Milk, creamer, broth, juice, alcohol |
| Appetite control | Hot tea, decaf coffee, seltzer, cinnamon tea | Sweet drinks that trigger cravings |
| Training days | Water or black coffee pre-workout | Sports drinks with energy (save for during/after training) |
| Long fasts | Water, mineral water; add unsweetened electrolytes if needed | Any energy-containing drink |
| Blood sugar goals | Zero-energy choices | Sweetened coffee, milk tea, juice |
Safety Notes
Fasting isn’t for everyone. People who are pregnant or breastfeeding, under 18, with a history of eating disorders, or on certain medicines should not start a fasting plan without medical guidance. If you take insulin or sulfonylureas, ask your clinician about dose changes before you change meal timing.
Bottom Line Rules You Can Trust
Drinks that add energy end a fasting window. Water, black coffee, and plain tea fit between meals for most plans. If you choose diet drinks, go by outcomes: appetite, cravings, and lab results with your clinician. Keep the plan boring and repeatable, and your body will do the rest.