What Causes Vomiting After Taking Medicine?

Hi, yesterday I went to immedia care clinic for a sore throat that has lasted since sunday. I also had night sweats, and a little bit of a headache. The doctor ran a strep test and it came back negative. So, he prescribed me a Z pack. I took the first two pills yesterday and then this morning I took the next dose. I also went to get some food, I didn't each much of it (MCdonalds mcmuffin and hashbrown) then about two hours later I threw up. I'm not sure if it was because my stomach couldn't handle it or something else more serious. What are your thoughts?