I had a class right after practice this semester. Literally had to jog to get there. It usually was not awful, especially because it was a lecture-based class with very little participation, but some days were brutal. If a tough workout (especially on a hot day!) would run long, it wasn't unusual to sneak into class late and end up sweating bullets for the first 20 minutes. Then my paper would get soggy and my shaky handwriting definitely showed. For the most part, I'm pretty sure the timing of the class didn't affect my grades. Getting up for that 8 am class would probably be much worse, especially if you sacrificed breakfast to make it there.
Then again, you'd also have to take into consideration the professor. I did have a foreign professor that had a huge aversion to wearing sweats and bringing drinks to class. Definitely had to clean myself up before walking in there!