If you can’t afford glasses or are in prison or an orphanage or some place where they’re not available, you’d just have to use distance. Focus on a spider on the wall of your cell or anything you can find that’s at your blur horizon.
If you had access to reading material you’d want to get as much distance on it as you could (print pushing.)
I think you’d still improve under those circumstances especially if you got adequate sunlight out in the yard or on the chain gang.
The lenses are a rather modern invention (compared to say fire, or agriculture) and most people through most eras never wore them. Myopia used to be pretty rare.
Probably the biggest single thing you could do, in the modern world, would be to ditch the smartphone or other tiny screen. I think with good attention to eye hygiene you’d improve. The lenses are a crutch or convenience so that you’re not wandering around tripping over things while you’re getting your vision back.