I'm trying to get my 2 year old to ditch the sippy cups but when he gets regular cups after he is done drinking he tosses the cup like he would a sippy. So I'm thinking about getting him something called Sassy Grow Up Cups. It looks like a regular cup but it doesn't have a lip and it's not suppose to leak cause it has a stopper in there. Has anybody used them before? This is what they look like.