Boyfriend overly sweaty

So, I know this isn't about a girl thing and all. But I am straight up losing it!! My boyfriend and I have been together for almost two years, and every night (no matter what the temperature/time of year) he sweats like he's in the f*cking dessert in the middle of the day!! And what's worse is it smells like vinegar! He says this is a thing he's gone through all his life, but this is ridiculous! We could have only a sheet on us, or an entire army of blankets. It's honestly worrisome and becoming a bit too much for me. What should I do to help him, and our bed/sheets?!