Smelly sheets

My SO tends to sweat in his sleep and causes the sheets on his side of the bed smell. He doesn't put on a bunch of blankets. He just tends tends to sweet. I is resistant to washing the sheets every week (we have to go to a laundry mat) even after I tried to tell him about the smell in a nice way, but he seems to get slightly offended when I talk to him about anything that has to do with body smells. What do I do?