Tbh we wash them and use them for really dirty stuff. Like when you need to remove mold with a chlorine spray or poop from your shoes. Then they get tossed because there's no way I am washing that again.
We're phasing out single use sponges though, but now I don't know what to use for the really dirty stuff.
We use a combination of brushes with wooden heads (I don't like stuff with handles though), structured cotton towels from the drug store, and sponges from Ikea called "Pepprig" which I think work best for most things. They are also plastic but you can wash them easily.
Same. We actually cut them in half before we use them (no this is not a way to save up $10k in a year) and then quarter them when they turn to crap sponges xD