I serve milk with meals and they each have a water cup on a specific shelf that they can go get a drink from at any time. At meals they get their serving of milk and then water. Occasionally if they want more milk I will allow it IF they are eating well. If they just want to fill up on milk that's a no go.
What I, personally, would do is give him his serving of milk with his meal and when it's gone I would give him water. If he eats, he eats. If not, he doesn't. But I wouldn't allow him to fill up with just milk. He won't die if he's hungry. My kids eat every 3ish hours so it's not like there's a looooong gap between meals. Though admittedly if the kids are super active I will give them a few crackers between breakfast and lunch otherwise 1/2 hr before lunch becomes the witching hour.
I don't know what your regulations are but here we cannot allow a child to walk around with a cup or bottle. It took a little while with some kids to 'get it' that their water cups need to stay on the shelf (take a drink then put it back) but my youngest right now is 16 months and even he knows it goes on the shelf after taking a drink. It helps that the kids will police others who don't put their cups back.
