At 14 months I assume your son still eats in a highchair or other restrained booster seat. It is time for him to receive his milk primarily at meals and not at-will throughout the day, so to start his transition, simply do not offer ANY other liquids between meals. None at all during this short interval, not even water. This means that he will get very thirsty and with only the milk available in whatever container you next wish him to use, he will simply drink it! If you are very firm and do not offer other juicy items like applesauce either to replace the fluid, this will only require a few meals to settle down. We had a son who at that age wanted no solids AND would only use a bottle for his copious drinking of milk, so we had to do something as he was too big to get adequate nutrition from only his gallons of milk, and this worked. If your child is anything like ours was (i.e.with a will of steel) and desires nothing but his bottle for his milk, he will hurl it to the floor when you start this and fuss and possibly tantrum on you. But it is all for YOUR effect, therefore, place him in his seat and be sure he is safe, remark that he's such a big/nice/wonderful boy (or whatever), do not mention the milk cup, place the milk in a sippy or straw-type cup AND LEAVE THE ROOM. Peek back at him in a manner he can not detect. If he throws the cup, return with NO COMMENT, place it back on his tray and leave again. Repeat. You will soon be surprised when you peek, that he is slurping down that milk because he is thristy and can evaluate that he has to help himself....!