I started offering sippys around 6 months but TBH neither of my boys drank much out of them until after a year, and even after they knew how to drink out of the spout they still always wanted me to hold and tip the cups for them! We had a lot of luck with straw sippies for both of them. My DD is 7 months now, and she just chews on her cup although I do offer it every day for practice. A lot of BF LOs do well with straw cups. I think it's ok to keep offering sippies, and try different kinds for sure, but don't stress too much if he doesn't seem to be drinking much out of it yet. If it is hot and you'd like him to drink some water, what about trying an open cup and helping him with it?