My son would drink a TON of milk, but would also eat. When I started taking issue with his fluid intake was when he was setting through his diaper every night.
What I started doing is telling him he could only drink milk at the table (and juice, but that was never a HUGE issue).My DS is also 3 1/2 and hasn't had milk before bed in about 6 months. (Okay, on occasion, when we have an early dinner, he still gets milk before he brushes his teeth and goes to bed, but that is rare.)
He was at one point drinking two 8 or 9oz cups of milk before falling asleep, then asking for another at about 4am. The first 2 weeks of "No bedtime milk" were hard! I HATED THEM! I Wanted to give in! Sleep was so much better than fighting! But... now it's a non-issue. He is allowed to have as much water as he wants up until about 7:00 pm (We are all night owls, so he is up until at least 9:30 most nights), then only little sips if he REALLY needs them. I have a cup of water I keep next to the bed for myself, and he will sometimes wake up and come ask for a drink of it. I won't let him have his own, because of the night time peeing.