I sweat - a lot - during and after a workout or sex. The hair on the top of my head sweats... It's not a problem that a doc can fix (hyperhidrosis) without doing stupid things like trying to take out sweat glands under your arms. Some people just sweat more than others, it's something you get used to. After many a workout (like on our "cold" winter evenings here in so cal) my husband is dry, he's a black muscle bear and lifts as hard as I do, but I'm wet from head to toe, wiping sweat off the benches and always leaving in wet cloths.
"I very much doubt that it is a medical problem. Try taking the coldest possible shower and stay into it long enough to cool off."
I agree, take a cold shower, cool down. I like cold showers because it shuts down the sweating - for a while. But you may start sweating again with any exertion (walking fast for example). Cool weather/AC of course helps. But dam I can get sweaty in a closed coat if I don't unzip with exertion.
So, it seems obvious but keeping your body cool is the best advice. Wear a light shirt, etc. I don't see how guys can wear an undershirt, I cook when I've tried. Anyway, just stay cool and go slow to not sweat.
A note on sweating and sex. Of course we sweat from the exertion of fucking but maybe being completely covered in sweat during sex is a defense against getting caught, that is if someone were to catch you fucking their partner but since you're covered in sweat you can slip from his grip and run.