Hi J. --
We have a 22 month old, so we went through what you're dealing with last summer. I started introducing the sippy cup with juice or milk with the spill-proof piece attached. Some days he was interested and other days he wasn't. I just made sure I always offered it first. If he didn't drink out of it, we would give him the bottle. At 15 months, he was still favoring the bottle, so we went cold turkey. He went without milk or juice for a few meals, but it didn't last long. He figured out that if he wanted something to drink, he needed to learn to use the sippy cup. We tried all varieties of sippy cups and found the Gerber ones to be the easiest for him. You will be amazed once your child gets used to it, the bottle becomes a non-issue. At least for us, that's how it happened. We were recently at my sister's home who has a six-month old. Our son saw the bottle and said, Baby bottle. He had no interest in it at all.
Good luck!!
T.