I remember having this trouble with one of my children. I think I put watered-down juice in the cup (which she had never had before) and then coated the sippy cup lip with pure juice. Once she got a taste of the juice on the lip, she figured out how to get at more of that sweet stuff. After that lesson, it became a novelty to drink from the cup and I never had to use juice again. Oh -- she hated the Nuby and couldn't really get the hang of it. I think we used Avent and then I switched to Playtex because I hated the leaking of Avent.