These days dishwashing liquid is antibacterial so the sponge tends to last longer than it use to IMO. My "silverware" ... cups and stuff (toothbrush) hang from a tree in a mesh bag but the soap and sponge go elsewhere in an open upside-down bag so the sponge can dry, somewhat. (I can dream at least.) In any case, I don't want that sponge anywhere near my toothbrush.

I have always used a water bottle cozy that I'd keep wet in warmer weather. Now with all summer trips it's always wet and bacteria poop will normally noticeably sour it in a few days. I don't expect it will kill me either but I can only ignore it for so long so I've gone the bleach route by repurposing a little, maybe 1/4 oz bottle that once held eye drop something or other I noticed in the recycle bin one day. I've been watching for a nice bottle twice as big for soap as that would last me two weeks easily.

I'll throw the sponge in the bleach bath too just cuz I can I guess. It's still not going near my toothbrush.

I am amazed the cozy has retained its color over the years. I was actually hoping it would get a few shades lighter by now but you only need a drop or two per 1/2 quart H2O to fix the smell.

If I remember correctly, bars and restraints use some sort of sanitizer that I expect might work too. Don't know if there's any advantages or not. Just a possible option if available.