I will say I don't struggle as acutely as you with this, but most days I do struggle to get out of bed and get myself presentable so I hope my advice still helps.
Usually I try to knock out all my hygienic needs in the shower, if it's really bad I'll sit down in the shower. I'll brush and wash my hair, brush my teeth, and clean my body all in one session. Then I'll put in all my hair products.
I don't know what hair type you have, but unless your hair is super straight it probably will look fine if you don't brush it for a while. Regardless, buns and hats or beanies can help cover up if it's a little messy. If you absolutely don't have the capacity to shower and you still need to be presentable, "bird-baths" are my go-to. Just wet a cloth and add a (tiny) bit of body wash or whatever you use, then wipe down important places like your armpits. Always put on deodorant, and if you like perfume just put a little bit on (don't try to mask anything with it).
This part is optional, I don't know if you wear make-up, but if you do on your better days and like how you feel with it on, it can make you feel more confident (at least that's my experience, everyone is different). A tiny amount can go a long way with how you feel about your appearance. While still sitting on the floor, I'll put a bit of concealer under my eyes, blush, and tinted chapstick. It just makes me feel like I look more "alive".
These are just short-term tips I have from my years of being depressed, I think Line's post above is a great advice for getting better in the long term. I'm still working on getting there myself and it's really hard, so you aren't alone. I hope your situation improves <3
