How would you deal with a subordinate who has a constant strong body odor?

1989, had a guy we called pee pee peeler
Came in, donned gas mask, Lysol and scrubbed him down

I had a roommate when I was a young SP4. He was a Private and didn't do laundry or shower on a regular basis. I complained to my SL about it and he told me I was a SP$, take care of it. He also told the Private he had to do what I told him. After PT, he was told to shower, at lunch, another shower, after work, laundry and another shower, before he went to sleep, another shower, after a few weeks of this routine, he figured it out!

One way I handled it on one occasion I took the individual aside, mentioned the BO problem and sent Him back to the barracks to shower and put on a clean uniform then return to work. It never happened again after that.

Professionally tell them to wash their "uniform" or change out their boots...

Never had a subordinate with issue because telling the guy to wash his stink was enough to cure it. Peers on the other hand...back when we had a community head, the LCpls in the platoon gently carried our brother to the shower and bathed him with scuzz pads and Palmolive. He got the religion quickly and never smelled again.

Investigate the root cause. It could be an outward sign of depression. Best to find out why, before implementing a fix blindly.

I would take them aside and ask them if they have a medical problem or that they maybe need to address this as it is noticeable. Maybe an antiperspirant instead of an anti deodorant.

A bucket of soapy water and a scrub brush?

While I can't find anything specific, I would recommend you contact your ships medical and legal departments.

I was in the process of getting discharge paperwork done on one of my troops. When he went for a required medical examination found out he had a food allergy and that's what was causing the horrible smell. After a few weeks of no starch diet the smell was gone and I felt like an ass.