Getting rid of the bottle!

I was talking with my siter-in-law and she told me about her struggles to get rid of the beadtime bottle with my 16 month old nephew. During the day he is completely content with his sippy cup, but at night he howls for the bottle.  I personaly didn't have this problem with my oldest (we'll see what happens with the next!). She basically decided one day she was just over it and never looked back. Does anyone have some advice?