when you do a water fast you should only consume water. electrolytes like magnesium, salt, and potassium are okay depending on what sort of climate you live in
supplements are completely out of the question, even things like multi vitamins
Multi vitamins have no calories and will break a fast. So will herbs and other supplements. don't get caught up with the calorie bullshit. a diet soda has no calories so do people actually seriously believe it is okay while fasting? use logic here people
things like citrus actually contain calories but they won't break a fast if you squeeze some lemon in your water. so no it isn't about calories
i see a lot of these social media guys pushing BCAA's during a fast. you are wasting your time if you listen to them, they are just trying to sell you their garbage