I always see sippy cups advertised as "spill proof." How about "backwash proof", I mean look at this. How do you even get that much food down through the valve and straw!? Which brings me to:
Parenting Truth #342: At some point you will be thirsty and your child will have a drink. You might think, "Hey, I can just take a sip of his/her drink." Don't do that. See the picture below? This is with a sippy cup, it can be even worse with a regular cup. You do not want to drink after your children. Ever.