Whats the best way to break my 17 month old twins from the bottle? they only use it when going to sleep

Wean: I would recommend you slowly wean from milk or formula to water, they generally lose interest once you get to 3/4 water, but at least it won't risk their teeth! you mix a little more water with the milk every week, general if you use 4 oz of milk, then start with 3 oz milk to 1 oz water, then go to 2 and 2, and finally to 1 milk/3 water, it may take a week or so at each step. Good luck!