Putting drugs into someone's food without their knowledge is a crime. Did you know that if you drink on Antabuse it's possible to DIE? So if he thinks he's simply safe to drink because he's not taking it, you could literally poison/kill him?
I think it's a terrible idea for you to have ANYTHING to do with whether he takes it, but if you want to be the nurse/warden, I guess that's up to you. But do NOT sneak it into his food.