[Our little lounge lizard]
She's done great with drinking water from a sippy cup, but whenever I would put her formula in it she'd look at me like I had two heads. Absolutely NO interest. We decided that a more firm approach was needed, so we withheld the bottle completely and only offered the sippy cup. She still wasn't interested so at the suggestion of a friend we went out and bought a different kind of cup.
It's called the three-stage sippy cup by Nuby and it worked like a charm. It's shaped like a sippy cup but has two different spouts - one shaped more like the nipple of a bottle and one more like the spout of a traditional sippy cup. We tried the nipple-shaped spout and she took right to it. The third stage is removal of the handles, but we're not too worried about that part as she does fine with or without them. I just thought I'd pass along the recommendation for anyone who is having difficulty transitioning their toddler from the bottle to a sippy cup. Now I may have to buy a few more so that I'm not constantly cleaning this one!