What am I doing wrong with these sippy cups?

DS uses the Nuby straw sippy cups and every cup we have/had always leaks when it is on it's side. I even tried the Munchin brand and same with those. I have no clue what I am doing wrong but the are definitly not spill proof. Does anyone else have this problem?

Re: What am I doing wrong with these sippy cups?

Sometimes this would happen when I screwed on the top too tight. The liquid would also back up through the straw.

Re: What am I doing wrong with these sippy cups?

Yes, this happens to us all the time. I even bought new ones, and still the same. I will try what the other poster said, not to tighten them too much.

Re: What am I doing wrong with these sippy cups?

Have you tried the Nuby sport straw ones? I find they don't leak at all!!


The other Nuby's used to leak on me too...

Re: What am I doing wrong with these sippy cups?

I am gonna try the other ones and try not to tighten them too much. The only other thing I can I think of is that from he throwing them or dropping them off the high chair he broke it.