When they asked (which was only sporadically) or when they were ill and I wanted to be sure they stayed hydrated, I just gave them a small plastic cup. 4 -6 oz. But I only filled it half full, or less.
I generally found that they only drank whatever they sipped before they fell asleep (when if they drank it all, they were awake and so was I, so they could ask for more). Once they fell asleep, they stayed asleep. The rest would still be there in the morning.
And as the others said, it's just water. A little spill on the sheet/blanket will dry, and a little spill on the rug will, too. I found my kids to be very careful, because they wanted the privilege of having the cup in there in the first place, and they didn't want to waste what they were allowed to have.
My son rarely asked for water. My daughter was the one who always wanted a cup on her night stand. She was between 4 and 8 when she seemed to "need" it the most (again, once she fell asleep, she never drank any more). She just liked knowing it was there.
I rarely wake up during the night. Once I'm out, I am out. Of course, I am perpetually sleep deprived, too, so that "helps". ;) About the only time I wake during the night is for noise (the dog barking at a deer in the yard, or if one of the kids gets sick and needs me), or if I am sick and my sinuses dry out, or are flowing and I need to blow my nose...which maybe happens once or twice a year.
So sorry that you do not sleep well.