So I posted a similar a comment a week ago and have been trailing this myself. I think once you get used to it is is fine. But a few things I noticed was that I needed to reduce my salt intake a lot and I can’t always be super strict. For example I often burn up in the night (health problems) and start the day already dehydrated and wouldn’t manage the whole day without water. A more relatable example could be if you spend the day outside and it’s very hot, you might need water before 20 hours, respect this and drink. All day water fasts are still fantastic.
Not sure about the gym stuff but I am very active all day, walk 10-20km plus move about all day at work. I think muscle mass and strength should be fine.
I do about 15-20 hours dry fast daily. It took about 2 weeks to adapt and be able to run and do exercises like normal. I did stop eating (or at least adding) salt to my food and increasing the amount of fruits (juicy foods) I eat. When I do eat I have little desire for dense, dry foods and get full and satisfied on very little.
I found myself doing intermittent dry fasting more because drinking water in the day would trigger hunger pangs. I much prefer dry fast as I feel I lose weight quicker and more weight is lost. However, I do feel that I become a bit more bloated when I don’t drink enough water and wonder if having a 2hr drinking window and a 1hr eating window, would be better for me.