Drink as much as your body asks for. Depending on how long you’ve fasted will affect this. Some people drink their water through food like fruits, others consume some form of drink
Personally I wouldn’t. You won’t die without a protein shake, especially with such a short fast
Yes. 72 hours isn’t that long without food honestly
If you’re doing intermittent you have no reason to worry about loss of muscle mass. 13 days would be different
Dry fasting is a killer of loose skin 👍🏻
You won’t lose muscle going on long fasts, you lose “protein” but not muscle. You go into autophagy which is your body breaking down and using old bad functioning cells and tissues for food - one benefit is no loose skin, because your body will make use of the extra skin tissue. Your muscles May look smaller, only because they’ve run low on glycogen, they’ll pump back up when you start eating carbs regularly. I’ve been water fasting for a long time but am new to dry fasting, but most the principles are the same, dry fasting is just accelerated.