How do you give him water? We use a straw cup. I don't give her milk yet but she drinks water from it just fine. To teach her to use the cup I started with apple juice then diluted it to water. Now she just drinks water and milk. I did have to try a few different cups before I found one that she could use and was not too messy.
My son is 18 months and has been having boob for naps and bedtime and homo with every meal. I just put it in a munchkin straw cup.