You know ...
dd went through a "stage". She usually take medicine easy, but this one week .. NO WAY. What I did was I pulled it up in a syringe then I sat down on the floor with her and put a teeny-tiny drop on her hand. Then I licked it off with HUGE drama and made a game of it. I was licking everywhere ... in the face, in the neck, on her limbs, her tummy. So as she was getting into the game I told her that she has to drink some before I lick her and eventually we got everything down.
Dont' know if it's going to help you ... might try.
Try giving in the bath, or sneaking it in while he is watching TV