Of course, I could. I take b/o seriously.
Yes i have, and i think they know they have b.o. Issues
I basically lie so their feelings won't be hurt and I say "I think you have been around some people that have body odor and the smell has gotten into your hair and in your clothes. Maybe they have been smoking or didn't wash their clothes. I just wanted you to be aware so no one will say anything to you that may hurt your feelings since it's not your fault".
Easier just to say to them : Hey ! Did you step in some dog doo? Sure smells like it around here !
I have. I just talked to them away from everyone else and told them that the climate in Florida was more humid than were they moved from so it made people bit sweatier and they may need to take an extra shower each day to compensate.
One time my friend told me that someone at his job had complained about his BO so I saw that as an opportunity to tell him the truth: Sometimes you're a bit "pungent", maybe try a stronger deodorant? Lol
In facts I used to tell my best friend this. I think it depends on how much closed they are to you. Of course after telling them about their problem. You should give some ways to treat their body odor.
If you don't know much about those ways, I think this article is useful for you: authorityremedies.com/home-remedies-for-body-odor/