I have only had the problem one time with my ds when he was much younger and had an ear infection. He couldn't stand the taste of the medicine and it would make him gag, ceftin I think. We went back to the dr and got a different one and he was back to taking it fine. If it isn't the taste, I would just tell him, we need to take this medicine and we are not doing anything until you take it. I know you don't want to take it but, you are sick and you have to take it so, tell me when you are ready.
Also, I agree with trying the cup too. I remember awhile back other M.'s saying that worked for them.
good luck
ps. a warmed throw pillow from the dryer feels good to lay on when an ear is hurting.