This is easy to remember, since it's a short list.
- Water of any kind, including sparkling and mineral, just avoid any that contain fruit juice or sweeteners, even stevia. Some experts say you can have a slice of lemon in your water or a splash of apple cider vinegar. If this is necessary for your compliance, go for it, but if not, drink it plain.
- Black coffee is allowed, just avoid cream or sweeteners (both sugar and sugar-free sweeteners) — this includes Bulletproof Coffee.
- Herbal tea.
Avoid BCAAs, smoothies, protein shakes, sports drinks, and bone broth. Fasting expert Jason Fung, MD, a nephrologist (kidney specialist) and author of The Complete Guide to Fasting, told POPSUGAR that even chewing gum can "produce an insulin response." The point here is that if you take in calories, then you're not technically fasting.