I've really only had this happen once, when a nurse I worked with always cames in reeking of garlic. When I say always, I mean every single time he came to work, which was 5 nights/week. It was SO strong, there was no mistaking it.
One night I couldn't take it anymore and just straight up asked him why he smelled like garlic. Turns out he was taking garlic "supplements". He stopped taking them--he said he didn't realize he smelled that way, and thanked me.
Whew! Granted, the approach I took may not work in every situation, but when it got to the point that our patients were noticing, I had to ask.
On the flip side: If I were a patient and my nurse smelled...not good...I don't think I would want them taking care of me. Why? Because the thought runs through my head "if they can't take care of themself, how can they take care of me?"
I'm sure I'll flamed for that, but it is my opinion.