The zoli leaks worse than any straw cup I have ever tried. We have had good luck with cheap nuby cups but DS bites holes in the straws so we had to switch to something with a harder straw. We are still on the hunt for the perfect cup but we have had good luck with the playtex insulated cups.
Although, I bought a second set online and they were very slightly different and super leaky. Not sure how to pick out the right ones other than by knowing what they look like, now.
Re: Straw cup recommendations
Emily 8.8.08
Madeline 1.2.11
William 8.5.12
if I don't put the cap on properly.