I’ve found that, for runs of an hour or less, I don’t need any water. Past that, though, things start to go downhill very quickly, and not in the fun “hey I’m running downhill” kind of way. I used to use a 24 oz hand-held model, but now I’ve advanced to a full 6-bottle belt (48 oz total).
Instead of just water, though, I use nuun tablets, every flavor of which is delicious. They’re more quickly absorbed than water alone, and have salt and other electrolytes to keep you feeling strong.