Of course, I haven't had to do this yet, but two things come to mind that seem automatic for me:
1. I can't imagine denying water to anyone, least of all small children, who can easily become dehydrated. Unless it keeps him from eating, I think that he should be allowed a drink every time his body wants it. His body is still learning that when it's thirsty, it can expect a drink, and I don't think that it should be trained to do without unnecessarily.
2. In my mind, what you're describing is all part of the change in sleeping habits/patterns that starts during pregnancy, sometimes not until after birth. Yes, we all need our sleep, but just three years in is still part of that no-sleep zone, same as getting up at night to feed.
When I'm up during the wee hours, I (sometimes) use that time to catch up on other stuff. There's one TV show that I have to watch when it's quiet. I watched it at 3:00 this morning before going back to sleep. Sometimes I get on up and take my bath, and then go on back to bed. I've gotten up and started on cooking, ironing.... I need to get my butt on the treadmill. I just use that time as if it's any time during the day to do stuff that I can't get done with a little one at my hip or breast. There's no such thing, anymore, as daytime and nighttime activities when it comes to stuff I can do at home. I just do whatever makes sense at the time while I'm awake.