Tea, coffee, sparkling and still water are all great options whilst fasting. However, some in the health and wellness industry do consume other options like BCAAs, pre-workout shakes and other supplements.
Adding a squeeze of fresh lemon to your water or a minimal amount of milk to your tea or coffee is fine, but the effects of caffeine may be intensified on an empty stomach, so be aware of your caffeine intake. The purpose of fasting is to keep your blood sugar levels low, so you can tap into stored energy, so make sure you're consuming as little sugar as possible.
For those of you interested in the purest style of fasting, and all the benefits; fat-loss, mental clarity, improved health markers, increased sleep, to plus many more, it's best to stick with water only during your fasting window.
If you'd like to learn more about fasting, which type of fasting method is best for you and how to fast correctly, check out The Fasting Playbook for more.