B.M.
depends on how clever you can be. Maybe water down his milk until it's pretty much cloudy water, but put the real good stuff in a brand new design sippy cup????? Then when he questions it do a "hmmmm. I guess milk tastes better now in this kind of cup".
Or if he's one of those critical thinkers just reason with him. it works for some kids, not for others. You say "look Johnny once you turn 2 - no more bottles. Let's pick out a big boy cup just for you". Let him pick out his special cups and make a big deal about him being a 'big boy now'. Then start replacing bottle feedings with a cup one a day for a week or whatever (as you practice for him to be a big boy so he's "ready" to be 2). so it's not really 'cold turkey' but by the time he's 2 you have gotten him 'weaned' off bottles.
the other choice is to stop buying milk for a while - 2 or 3 weeks isn't going to do him harm and he can get his dairy from cheese or yogurt etc. Then you guys can 'get rid of the bottles' because there isn't any need for them - no milk = no bottles. When you reintroduce milk the bottles are gone - so you ask "would you like milk in the blue cup or the red cup"? This still gives him control over where the milk comes from, just not from a bottle.