How old is your son.. Cause My son didn't start like these kind till about 16months. They have some Gerber Starters that my boys never had a problem with when starting off with a sippy cup.. I started them @ 9/10months
he is 7months. He has 2 other sippy cups and also the playtex one with straw that teaches them to drink from a straw and he takes these real well. I think I did buy the wrong ones though cause the mouth part on these are kinda big lol and he gets soaked