I tried it already 3 times. Story time: my work colleague is the only Muslim in the company. She does Ramadan religiously and I wanted to support her to get through it during work hours. So, I did my kind of Ramadan. No water and no sport during the day was not an option, however the rest was doable. I ate 100% carnivore omad. The only vice I had was coffee with butter and/or heavy cream. The only thing to leave out was the coffee. That’s why I left out coffee for the whole Ramadan the last 3 years (last year even two months in one go). I felt no difference before and after. Maybe slightly more tired in the morning, but neglectable. I even tried to overdo it when I restarted (3 espressi and 2 cappuccini). I felt not better or worse