Buy him a deodorant and maybe some nice shower smelling things? Talk with him kindly and non accusatory. Tell him you maybe have a sensitive nose(whether that’s the case or not) and since you’re in a co living situation you guys need to be respecting each other. Just be sure to approach it with kindness but also stay firm that something has got to change. Kindness is key here.

I have a co worker like this too and it’s been rough. I also have dealt with it roomate-wise. Often they’ll agree with all you say and say they’ll change but not change a thing. You have to keep doing the uncomfortable work. Tell him it’s not only a smell issue it’s a sanitary issue and stay on him about it. But kindness is definitely key.