He's six. He's perfectly capable of understanding that his ears really hurt, and if he doesn't want them to hurt again, then he needs to take the medicine. I'd understand this if you were talking about a two year old...but he's SIX!! My youngest had chronic ear infections and even at age two, she understood that the medicine would make her feel better. You really need to just stress that to him...that if he doesn't take it, his ears are really going to hurt very badly.
Just take a deep breath... :) ...and know that he CAN do it, and that this is just a little bit of silliness on his part. I know medicine can taste awful...but it's just a part of life in the modern world and we all have to do it. Pharmacies can flavor medication, but I've found that really doesn't help any.
If it really doesn't go well tomorrow, if he really won't take it...and I suspect he will if you really explain in plainly to him...ask your doctor for another alternative.
I couldn't get my youngest to take an antibiotic when she REALLY needed it...her ear infection got so bad that she had an open sore on her eardrum...they have antibiotic shots that hurt really bad and come in a series of three. (It may seem a little off, but maybe tell him if he doesn't take it, he'll have to have three shots instead?) I felt terrible about the shots, but she was only 12 months at the time and I couldn't explain to her why it was important...and yes, the shots did hurt very badly. Far worse that vaccines.
Good luck!