Yes, unsweetened Waterloo during a fast is fine for most goals, since it contains carbonated water and natural flavors with zero calories.
Thirst hits hard when a fasting window stretches on. Many people reach for fizz to keep things easier. A can of Waterloo gives bubbly taste without sugar or sweeteners, so it lines up with most fasting styles. The sections below spell out when it fits, edge cases to watch for, and smart ways to sip so your fast stays clean.
Quick Verdict And Why It Works
Waterloo is flavored sparkling water. The brand states each can has zero calories, zero sugar, and no artificial sweeteners. That pairing keeps insulin and digestive workload low, which is the goal during a fast. The only flavoring is what U.S. rules call “natural flavor,” meaning extracts or essences used for taste, not nutrition. In short, you get taste and fizz without energy intake.
Fast Goals, Drink Choices, And Fit
Not every fast has the same target. Weight management, metabolic rest, religious practice, and lab work prep sit on a spectrum. Here’s a crisp view of how common goals line up with plain water, plain seltzer, and unsweetened flavored seltzer like Waterloo.
| Fasting Goal | Drinks That Fit | Notes |
|---|---|---|
| Time-Restricted Eating (such as 16:8) | Still water, plain seltzer, unsweetened flavored seltzer | Zero-calorie fizz helps adherence without adding energy. |
| “Clean” Intermittent Fasting | Still water, black coffee, plain tea, unsweetened flavored seltzer | Avoid any sweeteners or creamers; flavor extracts without calories are fine for most. |
| Weight-Loss Window | Still water, plain seltzer, unsweetened flavored seltzer | Low insulin load supports the intent of the fasted span. |
| Religious Fast (varies by tradition) | Check tradition’s rules | Some allow only plain water; others restrict all drinks. Follow your guidance. |
| Blood Work Prep (fasting lab draw) | Usually water only | Follow the lab’s handout; some tests allow water and black coffee, many do not. |
| Dental Sensitivity Concerns | Still water first | Seltzer is mildly acidic; frequent sipping all day can wear enamel in some people. |
Drinking Waterloo During A Fast — Rules That Matter
Zero Calories And No Sweeteners
Each can lists carbonated water and natural flavors. No sugar, no stevia, no sucralose, no aspartame. That keeps energy intake at zero and avoids a sweet taste that might push appetite for some people. If your fast forbids sweet taste altogether, stick to plain water, black coffee, or plain tea.
Natural Flavor Means Flavoring, Not Food
Under U.S. labeling rules, “natural flavor” covers essential oils, essences, or extractives from plant or animal sources when used for flavor, not nutrition. In a fizzy water, that means trace aroma compounds without protein, carbs, or fat. The label doesn’t need to list every source, only that the function is flavor. See the federal definition here: 21 CFR 101.22.
Acid And Bubbles: Stomach And Teeth
Carbonation can feel gassy for sensitive stomachs. Citrus-leaning flavors tend to taste brighter, which often means slightly lower pH. Plain seltzer is usually gentle on enamel; flavored versions can be a touch more acidic. A few simple habits help: finish a can in one sitting instead of slow sipping all day, chase citrus flavors with a rinse of still water, and wait a bit before brushing.
Evidence Snapshot: Fasting, Hydration, And Adherence
People stick with a plan when thirst and cravings feel manageable. A light, flavored drink gives sensory variety without calories, which can raise adherence for time-restricted eating. Health agencies define intermittent fasting as planned periods of eating and not eating. Large academic guides describe weight changes and cardiometabolic shifts that can show up with time-restricted patterns and alternate-day setups. You’ll also see a steady theme: hydration during the fast helps people feel better and hang on to the plan. For a clear, plain-language overview of what intermittent fasting looks like and common effects, see this summary from the Harvard T.H. Chan School of Public Health.
Ingredient Label: What To Scan On The Can
Flip a can and you’ll see a short list. That list lets you confirm whether the drink fits your fasting rules.
| Label Line | Meaning | Fasting Impact |
|---|---|---|
| Carbonated Water | Water with dissolved carbon dioxide for fizz | No calories; watch for bloating if you’re sensitive. |
| Natural Flavors | Oils, essences, or extractives used only for taste | No macronutrients; minimal effect on insulin for most people. |
| Zero Calories/Sugar | No energy contribution per serving | Aligns with clean fasting rules. |
When Waterloo May Not Fit Your Fast
Strict Water-Only Windows
Some plans and faith-based fasts allow only plain, still water. Flavors of any kind would be out. If your plan uses that rule, skip seltzer until the eating window opens.
Sweet Taste Triggers
Even without sweeteners, a bright fruit aroma can nudge cravings in a few people. If a flavored can makes hunger spike, reach for plain water, black coffee, or tea during the window and save the fizz for your meal.
Reflux Or Bloating
Carbonation expands in the stomach. During a long stretch without food, that pressure can feel uncomfortable for some. Swap to still water if burps or pressure bug you.
Smart Ways To Sip And Stay On Track
Pick Flavors That Feel Neutral
Berry, watermelon, and plain lime often read as refreshing without a dessert-like vibe. Dessert-leaning aromas can push cravings in some people during a tough hour.
Set A Schedule
Line up one can for the midpoint of your fasting span and another for late stretch stress. That gives you something to look forward to without grazing all day. Between cans, stack tall glasses of tap water.
Mind Your Teeth
Sparkling water is far friendlier to enamel than sugary soda. Flavored seltzer still lands on the acidic side, especially citrus. Drink with a meal when you can, use a straw if you sip slowly, and give your mouth a water rinse after a can.
Electrolytes And Sweeteners Are Different
Zero-calorie seltzer stays within clean fasting rules because it skips sweeteners and sodium. Electrolyte mixes vary. Many add stevia or sugar alcohols, which some fasters avoid during a window. Others add sodium or potassium for training or heat. That can be helpful during long sessions, but it no longer matches a “water-only” window. Read labels, and match the drink to the job you need done.
Carbonation And The Scale
Fizziness adds volume in the stomach. That can blunt appetite for a short while, which helps some people reach the end of a long stretch. The effect is temporary. Since Waterloo has no sodium, it won’t add water retention from salt. If bloat shows up, swap a can for still water and check how you feel the next day.
How This Applies To Common Fasting Styles
Time-Restricted Eating
During the fasting span, unsweetened seltzer fits well. During the eating span, pair it with meals to soften any enamel concerns and to keep fullness higher without calories.
Alternate-Day Patterns
On low-calorie days, a couple of cans can help blunt appetite. On zero-cal days, treat it like any fasted span: flavor is fine for most people, but switch to plain water if cravings flare.
Religious Or Medical Fasts
Directions vary. Some observances allow only still water, or restrict all liquids. Pre-procedure rules can be strict too. When in doubt, follow the instructions you were given for that day.
Common Myths And Clear Facts
“Any flavor breaks a fast.” Flavor alone isn’t the issue. The concern is energy intake and sweeteners that can confuse appetite or gut comfort for some people. Waterloo brings scent compounds without macronutrients, so it fits most windows that allow coffee or tea.
“Carbonation ruins bones.” The bone claim mostly tracks to cola intake with phosphoric acid and poor diet quality. Plain seltzer doesn’t carry that pattern. If a doctor flagged a bone issue, follow their plan; the can itself isn’t the driver.
“Fizz always harms teeth.” Enamel risk relates to acid level and time on teeth. A quick can with a meal is far gentler than nursing an acidic drink all afternoon. Rinse with water and wait a bit before brushing to protect softened enamel.
Taste, Appetite, And Behavior
Smell and taste link to memory and cravings. A bright fruit aroma can make some people think “snack time,” while others feel satisfied by the ritual of cracking a cold can. Set up cues that help your day. If a certain flavor kicks off a snack hunt, save it for your eating window and pick a milder flavor for the fast. If fizz takes the edge off, keep a few cans cold and pair them with ice-cold tap water.
Many find that setting guardrails keeps the window tidy. Sip still water first, then have the can. Treat sips like breaks, not all-day background drinking. Stack your can with a walk, light chores, or a change of scene. The small routine keeps your mind off the clock while you stay on plan.
Buyer’s Checklist For A Fasting-Friendly Seltzer
- Zero calories on the Nutrition Facts panel.
- No sweeteners of any kind in the ingredient list.
- Short label: carbonated water, natural flavors, and not much else.
- No sodium unless you’re intentionally replacing electrolytes.
- Citrus flavors in moderation if enamel feels sensitive.
Simple Routine You Can Use Today
- Pick two flavors that feel neutral to you.
- Place two cans in the fridge for your fasting day.
- Set phone reminders for a mid-window can and a late-window can.
- Drink a full glass of still water before each can.
- Pause sipping 30–60 minutes before your lab draw, workout, or prayer time if rules require water only.
Bottom Line For Clean Fasting
Unsweetened, zero-calorie seltzer like Waterloo fits clean fasting for most people. It helps hydration, adds variety, and keeps energy intake at zero. The main caveats: strict water-only rules, cravings sparked by fruit aromas, reflux from bubbles, and enamel sensitivity during all-day sipping. If any of those apply, slide toward plain water during the fast and enjoy your fizz with a meal.
Sources: U.S. flavor labeling definition (21 CFR 101.22) and an overview from Harvard T.H. Chan School of Public Health.