You can eat normally during your eating window , but during the fasting window you should stick to very low‑ or zero‑calorie drinks so you don’t break the fast or blunt its benefits.

What you can drink while fasting

During your fasting hours, focus on non‑caloric or nearly zero‑calorie drinks.

  • Plain water (still or sparkling), with optional lemon slice or cucumber for flavor as long as you don’t actually eat the fruit pieces.
  • Unsweetened black coffee (no sugar, syrups, or cream; a splash of milk is usually fine for most people doing 16:8 or similar, but strict “clean fast” approaches avoid it).
  • Unsweetened tea (black, green, oolong, herbal) brewed at home; store‑bought bottled teas often add sugar.
  • Zero‑calorie flavored or sparkling waters that truly have no sugar, no calories, and no artificial sweeteners if you’re following a stricter fasting style.
  • Very low‑calorie broth (like bone broth, usually under ~50 calories per cup) is sometimes used in more flexible fasting approaches; it technically adds calories but may fit “modified fasts” or help beginners stick to the routine.

A simple rule of thumb: if the drink has meaningful calories, sugar, or sweeteners, assume it can affect your fast, especially if your goal is weight loss or metabolic health.

What you should avoid while fasting

These options commonly break a fast or work against typical fasting goals like fat loss and better blood sugar control.

  • Any drink with sugar: juice, regular soda, sweet tea, energy drinks, sports drinks, sweetened coffee drinks.
  • Creamy coffee: lattes, mochas, cappuccinos, or adding cream, sugar, flavored syrups, or sweetened creamers.
  • Diet sodas and artificial sweeteners if you’re doing a “clean fast,” since they may stimulate insulin or cravings for some people (more of a cautious/individual choice than a hard rule).
  • Alcohol in any form during the fast, because it adds calories, dehydrates you, and can disturb sleep and appetite signals.

What to eat during the eating window

Most intermittent fasting methods focus more on when you eat than on strict food lists, but what you eat still strongly affects results, hunger, and energy.

Good choices to prioritize:

  • Protein‑rich foods to keep you full and protect muscle: eggs, fish, chicken, lean meat, Greek yogurt, cottage cheese, tofu, beans, lentils, protein powders without added sugar.
  • High‑fiber vegetables such as leafy greens, broccoli, cauliflower, Brussels sprouts, cabbage, celery, and asparagus to help gut health, fullness, and blood sugar control.
  • Fruits , especially lower‑sugar ones like berries and apples, in reasonable portions for vitamins, minerals, and fiber.
  • Healthy fats such as olive oil, avocado, nuts, and seeds to support hormones and satiety (just mind portions, since they’re calorie‑dense).
  • Whole grains and legumes (oats, brown rice, quinoa, beans, lentils, chickpeas) for sustained energy and better appetite control.

What to limit in the eating window:

  • Highly processed snacks, fast food, and fried foods, which can make fasting harder by spiking and crashing blood sugar.
  • Sugary desserts and drinks, especially if weight or metabolic health are your main goals.
  • Constant grazing through the entire window; aim for balanced meals that actually satisfy you so you aren’t fighting extreme hunger during the fast.

Different viewpoints & flexibility

People use intermittent fasting for different goals (fat loss, blood sugar, simplicity, longevity), so their rules about “what breaks a fast” vary.

  • Strict / “clean fast” crowd: Only plain water, black coffee, and plain tea during the fast; absolutely no sweeteners, no flavors, no calories.
  • Practical / flexible crowd: Allows things like a splash of milk in coffee, zero‑calorie sweeteners, or small amounts of bone broth, especially for adherence and comfort.
  • Lifestyle / intuitive fasters: Focus mainly on eating windows and overall food quality; they may not worry about tiny calories in drinks as long as they feel well and hit their goals.

If you have medical conditions (diabetes, blood pressure issues, history of eating disorders, pregnancy, or breastfeeding), it is important to talk with a health professional before starting or tightening an intermittent fasting routine.

TL;DR:

  • During fasting: stick to water, black coffee, unsweetened tea, and possibly zero‑calorie drinks or small amounts of broth depending on how strict you are.
  • During eating: build meals around protein, vegetables, healthy fats, and minimally processed carbs, and try to limit sugar and ultra‑processed foods for best results.

Information gathered from public forums or data available on the internet and portrayed here.