HI! I HIGHLY recommend the Nuby Cup! This lil sippy cup is spill proof, which is GREAT, but thats not the best part! It's perfect to use with children who are learning to let go of their 'baba'. The spout on this cup also has to be sucked to get the liquid out...just like a bottle. It's a perfect transition from bottle to regular cup. I used it and it worked wonders! You can buy them at any major retail chain. I got mine at Wal-mart. Here is a website for them:
http://www.nubysippycup.com/
And this is what they say on the description:
NUBY SIPPY CUPS come in assorted styles and colors. The number one selling Nuby cup is the Nuby Sippy Gripper Cup shown below. This cup is an easy grip cup with a non-drip drinking spout. It is no-spill, has no valve, and you can turn it upside down and all around and it just won't drip.
Best of luck!!!