well done, funny how they jsut accept it, yep he'll test the limits just to see if there's one last hope, but stay strong.. if he wakes in the night, remind him, and offer him some water in his new cup and a cuddle.. ie remind him about the new cup and throwing the bottles away, then say that you will give him a cuddle and he can have a drink of water in there if he likes but he has to go back to sleep after that. remind him that milk before bed is a nice way to feel sleepy and relax and get snuggly, but that only babies need milk at night.. like his little sister, and that remember he is a big boy, with a big boy's cup and he can have a drink of water like mummy and daddy do if they wake at night. Wow what a big boy, well done.. (ha ha ha, as said a million times, am the queen of spinning bull.. well not really - just coaxing and praising and reassuring till they forget what the heck they were tantruming about. lol.. distraction and making them feel important and special.. works a treat.. especially cos well, once they get there and achieve that goal, they feel great and so do you. you might find that as well after only getting water .. which isn't as much a nutritional thing, his body might stop the habit of him waking so much at night as it's not getting the milk and top up of energy that it used to so will keep on sleeping (i hope so anyway.. that's what happened with ayja.
Good luck, well done and have a good night.