The Munchkin sippy cups
I recommend these for beginners. They are super cheap and I never had a leak unless he pushed it on the floor. That didnt happen until he was older so great for beginners. These lasted 9 months before they needed replaced and now that he is older he uses the hard spout cups.
Gerber's Nuk sip and smile soft spout
These are my current favorite. Now that my son doesn't need a soft spout he loves these. They dont leak and the lids lock on. They keep the liquid inside pretty cold for awhile but not as long as a thermal cup would. Super easy to clean :) and I love the cute patterns these cups come in!
Not every cup will work for every baby but try some out and dont invest in a lot until you know what works and what doesnt. I think its safe to say playtex has always been my favorite company to work with!