They didn't find anything wrong with him, so he got subcutaneous fluids and some anti-nausea meds. He spent the next twelve hours or so sitting in the spot where we left him on the couch upstairs. Then I couldn't find him, which really worried me. When cats are dying, they go hide. Thankfully, he'd made his way downstairs and up onto their perch.
He seems pretty normal now. Whining for his food. Glaring at us for not feeding him yet. All that Sam stuff. He's currently on a bland food diet of rice and chicken, which he's gobbling up.
Our neighbor left us another big bag of apples. I already had some that I bought, so it's apple central around here.