Sippy cup for 7 month old

Ok so my son just turned 7 months on the 30 and the dr gave us the ok to start him drinking from a cup but I have no idea which cup would work best. We have the munchkin 360 and a straw cup for our almost 2 year old but I don't remember how old he was when we introduced the cups. My 7 month old pretty much refuses bottles so it's hard to leave him with anyone. I was hoping he would do better drinking breastmilk from a cup so I could leave him with a sitter without feeling so guilty. What suggestions do you ladies have? Thanks in advance!