Took in a TNR, Melvin, he has liquid diarrhea, vomited, smells like poop. He is still eating, drinking but looks like he lost weight. I have not seen solid poop, but he also goes outside
Unless you can control what he eats, there may be things he is eating outside somewhere adding to his issues.
As far as meds, if you can crush a pill or get it in liquid form you might be able to add it to a bite or two of any of his favorite foods you do feed him, and then after he has eaten that, give him the rest of the meal. That way you know he's has taken all the medicine. If regular food doesn't work, try some canned tuna or chicken in water, lickable treats (there are several on the market to try), or even baby food meat (Gerber Stage 2 or Beechnut).