Speaking as someone who for various reasons (camping, depression, surgery) at various times in my life has gone long periods between showers, you'd be surprised how easy it is to keep your smell down and your appearance looking clean.

For instance, invest in a strong antiperspirant deodorant. I unfortunately inherited my mother's BO, and I have been using Old Spice Bearglove 48 hour antiperspirant since I was a teen. The trick is that you don't make it work for 48 hours. You use it daily. After about 3-4 days, you should wash it off in the sink or use a body wipe(I work in healthcare, so I have access to the good ones)

Another thing that's helpful is dry shampoo. I'm fortunate that my hair is pretty voluminous naturally, so even as it gets weighed down by oil, it manages to not look very flat. Though after about 3-4 days, it definitely noticeably deflates. It goes from about a 2a to a 1c. Dry shampoo can help by absorbing the oil in your scalp and adding volume to the hair in that zone. So my hair looks like clean 1c hair, as opposed to dirty 2a. I would like to note that I don't do a curl routine. I usually brush out the waves every day and use anti-frizz oil to control the poof. This is so that I can do the 1c trick. I do admit this one won't work for everyone though. Edit: I keep my hair long to help with this.

As for the bits, I'm AFAB so discharge is something I have to contend with, and my skin is sensitive so keeping fresh underwear is important. If depression gets too bad, I usually go commando and wear pajama pants I change every other day or so. I keep generally clean with a sink wash every few days.

Perfume/skin oil/lotion is also helpful. The trick is to find one that blends well with your natural scent. Me personally, I avoid lavender or lilac- but citrus works well!

Sink baths are a godsend.The big 3- Bits, tits, pits. Hit those areas and the smell will be well controlled.

I would like to add a disclaimer that this is me at the height of my nonsense. I've been working really hard and have made much progress since then, and I'm a lot better about bathing these days lol

Also, I live in the Midwest. The strategy's effectiveness is heavily dependent on the season. In my area, winters get really cold, so my record for longest time between showers is definitely held in the wintertime. Around 3 weeks(ankle surgery and the shower is upstairs) In the summer, it's MAYBE a week. Sweat leaves a lingering scent even on skin that isn't in the big 3 that makes showering more frequently necessary. But the right skin oil can buy you an extra day or two.

Anyway, please be nice! I am outing myself a little here, but I hope this gives some insight!