Believe it or not, Merino wool thong is the best I’ve found for sweaty work and workouts. Hard disagree with the cotton recommendation, cotton holds so much moisture and keeps it next to you, worst fabric for workout thongs. The wool is somehow miraculously not itchy, antibacterial, wicks away moisture better, dries much faster and doesn’t feel nearly as gross when you have to pull it back up if you go to the restroom to pee.

Second choice is a synthetic, but it’s a distant second. Cotton I never will again - it’s fine for work or relaxing at home but absolutely not for sweating.