when my little one was a little over two (so just recently now that i think of it) i got the teats out of the dishwasher and cut them up with scissors, then put them back in..... then when she was watching i made a big deal about 'ohhh look the dishwasher has ruined your bottle tops' etc etc, so she saw that they were ruined.... i then used her bottle with one of those green avent spout thingies, which previously she had refused to drink her milk out of.... but once she knew the other bottle teats were ruined and gone, she then reluctantly drank from the green spout, and now there is no issue....

it was very easy actually, i thought it would be a huge drama.... you just have to give them a valid reason why they aren't having their normal bottle anymore, so that they understand, anyways thats what i think.... did the same with her cot too, said we were giving it to a baby she knew, and she helped dismantle it.... in fact i'll probably use this tactic with everything, it makes a lot more sense than just taking something away that they love and hoping they are okay with it.