Some people just struggle with this type of thing. My eldest son has had an issue with BO his whole life. Even as an infant I'd bathe him in the morning and put him down for a nap and his hair would be crunchy from sweating.

He showers at least once a day, uses anti-perspirant and shower to shower powder. He changes his sheets every other day and washes his blankets at least once a week, his pillows every other week. He's clean, he just has a very strong body odor. He's tried every soap and body wash out there. He happens to be exceptionally hairy.

I don't know how I would deal with a friend with this issue, but with my son I let him know it's time to freshen up.