I had the same issue and we were at the point where our daughter was drinking more and more before bed and it was like her addiction to get to sleep. The first thing that I tried was only offering milk in the sippy cup, but formula in the bottle with the hopes that she would start to prefer milk and drop the bottle. However when she got upset or tired or really hungry she only wanted the bottle. I realized it was going to have to be cold turkey. Here's what I did and my pediatrician confirmed you do whatever you have to to break the bottle.
Day 1
In the morning I gave her her favorite breakfast right away so she wouldn't get hungry for the bottle. Then at her next bottle I gave her a piece of cheese first (to nip the hunger) and then introduced juice (watered down) for the first time in her sippy cup. The cheese-juice routined worked and I was sure to give it like 15 mins beofre her usual bottle so she wouldn't get fussy. Even before bed. The first night we ended up only giving her a couple ounces in a bottle right before bed.
Day 2:
No bottle and never again. My husband meanwhile was so upset that she was having juice before bed but i was simply amazed she was off the bottle.
Day 4:
Eventually we started offering her milk in a sippy and she would take that over the juice. Our doctor said it is easier to wean a kid off juice then the bottle so better to intro juice and then take it away once she likes the sippy. Literally 3 days later she didn't even need a drink before bed! And she now drinks like a quart of milk a day from a sippy.
Good luck!