You will have to make his life so bad with-o the medications that taking them is a much better choice. First though, has he said why he won't take them? If they are making him sick he may not have the right words to tell you. After that is established, medications cannot be negotiable.
I would NOT offer rewards of any substance for taking medications. Nothing more than a half spoonful of chocolate syrup - spoon YOU choose, lol. If he doesn't take them, he sits at the table - no food, nothing to do, no one to talk to him, (make getting up a really big unpleasant deal), etc.
IF, at age 10, he is allowed the power to refuse medications, you will never ever have any authority again. For the most part I agree with the collaborative problem solving approach, but not medications. Children do NOT have enough knowledge or sophistication to make medical decisions. Unless the medication makes him feel awful, or make him sick, then he needs to take them when you tell him to. It is a basic safety issue, in my opinion.
Can you lock him out of his room away from all his possessions and at the same time make sure that all the tvs, game systems, computers, etc... are inoperable? Maybe be able to confine him to one room with nothing to do?If so, use it. Tell him to either take his medications with-o full or spend however long it takes him to get over the drama and take them (in your sight, check to be sure he swallows) without giving you any problems, then he can sit here and he will not have ANY of his things.
He needs to learn that medications are a decision that parents make for kids. Kids have a right to be heard, and to express how they feel, but in the end they have to do what they are told my Mom and Dad when it comes to medicines and drugs. If he is getting sick, or feeling strange, it is important to call the psychiatrist to let him know and try to change to another medication that might not have those feelings/sensations.
Other than that is is a crucial battle - if a difficult child can make decisions on legally rx'd medications, he is a LOT more likely to make his own choices about illegal drugs.
My own kids have told me that medications are an issue they do not hesitate on if I tell them to take something (or not to). They know that if the medication is causing a problem, even a funny feeling, that I will work to find another medication or a dose of that medication that doesn't have the problem.
They also say they know that if they refuse after stating their concerns and being told again to take the medications, that I won't hesitate to grab pliers and pill them like the cat. (get control of their head/arms/whatever, push in on their cheekss until the mouth opens, use pliers to push the medications as far back as possible, close their mouth and massage their throat until they swallow a couple of time. Pliers mean no biting MY fingers!)
At this point it is not an issue, but each kid still believes it will happen - even almost 19yo Wiz!!!!!!!
If I sound too old fashioned, tough. There is just too fine a line between medications and illegal drugs, and too often our kids simply cannot get better and have full lives without medications.