When we transitioned our little one we tried sippy cups, we bought 500 million different types. We even let her pick out her own, nothing ever worked. We ended up trying one of the ones with a straw in it. She took to it right away and as time past we introduced the sippy cups again. She uses anything now: cups and straws! A few people I've talked to have had the same problem. If the sippys don't work, I definitely recommend to try a straw one =)
Good luck!