We use these cups: https://www.amazon.com/Playtex-Insulated-Twist-Click-Straw/dp/B001R1I44U/ref=sr_1_13?s=baby-products&ie=UTF8&qid=1297218280&sr=1-13
And quite honestly I hate them. They leak all the time. if the lid is on too tight, the milk or water comes out the top of the straw even if it is just sitting upright. If I loosen the lid a little, it leaks out the sides.
I very rarely use straw cups because of this reason, but would like to since I know they are better to use than sippys (at least that's what I've heard).
Re: Tell me about your straw cup that doesn't leak
love this one, I threw out all the others and replaced with these:
https://www.amazon.com/Nuby-2-Pack-No-Spill-Flexi-Colors/dp/B003N49ML8/ref=sr_1_2?ie=UTF8&qid=1297218712&sr=8-2
Savannah
Callista
Baby Trail Blog
"Someday we will look at our babies and know it will be worth it. If it was easy, we would not have had our babies, the babies we were meant to have." From Amy052006
We use these, too. Sometimes the straw will retain a little of the liquid and Alana will flick it (usually at me, lovely), but, the cups themselves never leak!
https://www.amazon.com/Nuby-Insulated-Spill-Straw-Colors/dp/B000BPPPL8/ref=sr_1_4?s=baby-products&ie=UTF8&qid=1297220075&sr=1-4
We started with those they were great. Then we moved to the playtex ones.
We use these b/c they don't leak! What we realized was that if DD sucked milk or liquid past the valve the pressure would create some bizarre vacuum and the milk would leak out but if we made sure there was no milk in the top part of the straw before closing it we were fine. That made all the difference for us.
We also use the take and toss straw cups at home. They don't have a valve at all so they will most definitely leak, but only in the "turn it upside down" obvious way.