My youngest son was breastfed exclusively for the first year of his life. This was not by choice either! He would just not take the bottle, not even with pumped breast milk. At a year I stopped nursing (a whole year, non-stop, I was ready!!!) I tried to give him a sippy cup, every size, type, color and shape I could find, but like the bottle, he would just not take them! I ended up giving him a regular cup. I bought small 8 oz plastic cups and I would put just a sip in it at a time; to reduce the number of trips I had to make to the fridge, I would pour a full glass and pour a sip at a time into his cup. It was frustrating at first, but honestly it ended up being a blessing. I used sippy cups with my oldest two and probably bought a hundred or so as they would always mysterious go awal. I would sniff out misplaced sippy cups by the smell, and I when found them under the couch, behind the T.V., in the toy box, under the seat in my car , oh I could go on and on, I would have to throw them out because they were so gross! (smelly, sour, cottage cheese milk, yuck!) I swear one is still hiding in my house somewhere, there is a smell in my kitchen that I just can’t eliminate (although, I wouldn’t put it pass my recently estranged husband to have hidden rotting fish in the curtain rods lol) Seriously though, I have no words of wisdom to offer on how to get your son to take the cup, I failed miserably in my efforts, but I did want to offer the alternative solution that I ended up using and that has been reasonably successful (although, I have recently bought stock in Bounty!)