If you mean intermittent fasting , the safest default is: water, plain sparkling water, black coffee, and unsweetened tea. Those options are generally considered fasting-friendly because they add little or no calories.

Usually okay

  • Water, still or sparkling.
  • Black coffee, without sugar, milk, or cream.
  • Unsweetened tea, such as green or herbal tea.
  • Diluted apple cider vinegar in water, if it agrees with you.

Usually avoided if you want a “clean” fast

  • Sugar, honey, juice, milk, cream, and protein drinks, because they can add calories and may affect the fast.
  • Artificial sweeteners, if your goal is the strictest fasting approach, since some guidance warns they may trigger metabolic responses.
  • Bone broth, MCT oil, butter coffee, and other calorie-containing drinks if you want to avoid breaking the fast.

If you are breaking the fast

Start gently with easy-to-digest foods like eggs, yogurt, soup, cooked vegetables, or avocado.

If you want, I can also give you a simple “allowed vs not allowed” fasting list for:

  • intermittent fasting
  • religious fasting
  • fasting for medical tests