Trying to get PK to drink out of a sippy cup has been a STRUGGLE! I own at least 3 or 4 different sippy cups plus one of those water bottles for toddlers with a built-in straw. She did not want anything to do with any of them. That, added with the fact that PK will drink neither water nor juice, has made trying to get any liquid into her quite the challenge. She does still drink formula, but the amount has significantly diminished. We're lucky if she manages to drink 120ml during the day nowadays.
But alas, it appears that things are finally turning around on this whole sippy cup situation. I finally managed to get her to drink out of a Born Free sippy cup. These things are great because they have no valve. I honestly don't know how a kid can learn how to drink from a sippy cup with a valve. It involves some serious sucking action. Anyway, she always pushed away the born free sippy cup, until one day, I tied down her hands and while her mouth was open, I squeezed a drop of pineapple juice into her mouth. She LOVED it! So much so that she took several sips of it before pushing it away. Since then, I have replaced all of the nipples in our Born Free bottles with the sippy cup spots. So now she drinks her formula out of these new spouts, and drinks it pretty well (when she decides to take formula, that is). We use the 9-month spouts, which are free-flowing.
Overall, she mostly still drinks formula, and if she's REALLY REALLY thirsty or hungry, I can sneak in some water. She will also occasionally take juice, but really doesn't like it when I dilute it. Arrrrrrrrrrrrgh...smart cookie! Anyway, I'm just glad that I'm making progress. At last!