As of late, I've been completely fasting during the fasting period; no water or any sort of beverage, except if I plan to workout during the fasting period, in which I try to gorge on water hours before hitting the gym. Dunno if it's detrimental to completely abstain from water during the fasting period, but I honestly don't have much of a thirst for water, so I skip it if I'm not thirsty.

Twice I've fasted for 24 hours, mainly because I didn't have an hunger at the time to eat any dinner during the evening. I also made sure not to hit the gym during those periods because I didn't think I could test myself to that degree.