J.C.
Tonight before he goes to bed, explain to him that the bottle he's getting is going to be the last one and that from now on, he will be drinking from a sippy. When he finishes with his bottle, take it from him and throw it in the trash while you're holding it. Make it exciting by saying "Say bye bye bottle!!" and waving to it. Then, after he's in bed, take the rest of his bottles and throw them away too. Take the trash out so that you can't be tempted. Then, starting the next morning, fill up a sippy with milk. If he doesn't take it, don't force him or get upset, just say "okay, I will put it in the fridge for later". Then, everytime he asks for a drink, offer the sippy to him. If he refuses it again, say "okay, I will put it in the fridge for you for later." If he goes the whole day without drinking, he will be FINE. Do NOT worry. He WILL drink when he gets thirsty enough. Stick to your guns. If you do, within a matter of a day or two he'll be transitioned. If you give in, you automatically set yourself up for days and days of him screaming and throwing fits to try and get you to give in again.