Repost...night sweats

Sorry to repost, but since I posted this before the weekend, it may have been easily overlooked!

My friend wakes up soaking wet with sweat in the middle of the night nearly every single evening. He puts out so much heat that I can feel it radiating off of his body if I go to bed after he does. Any thoughts on what could be causing that or what can be done about it?

Thanks in advance.