What's working for me right now is cheap American sliced cheese. Guinness has to take quite a few Benadryl for his allergies. Also chicken nuggets work well too.

Another thing I've noticed is that sometimes he won't take it if "he's the only one". Sometimes I have to cut the cheese slice into four little pieces, then hide the pills in one of the pieces (he doesn't see me do this part), then eat a piece while he's watching. Then I guess he thinks it's safe for him to eat. How I love being the food taster for the king! Actually, I hate it, cause that cheese is icky, but gotta do what I gotta do...

Perhaps you could try those meaty pill pockets? I think I've seen them at Petsmart. Good luck!