Keep your kitchen sponges clean, bacteria-free, and smelling like nothing at all with this handy trick. Once you're done cleaning with the sponge, wring it out and set it in a window. The sunlight will dry the sponge out and kill most of the smell-inducing bacteria. I prop my sponges up so that only one small edge is touching and all the large sides are exposed to air. This method works much better than chemical or microwave-based approaches. I have literally used a sponge until it shredded and it never smelled bad.
I never get a smelly sponge, even though they basically stay wet most of the time. Since I don't scrub the sink, the harshest detergent or soap my sponges get exposed to is dish soap, so it isn't getting sterilized from cleansers.
This is what I do:
Leave soap in it
That's it. When you are done washing. Rinse the sponge out. Put some clean soap on it and squish it in. Then leave it like that.
It doesn't waste. You use the soap next time you use the sponge, and I guess the bugs don't like being in soap, cause I never get any smell.
I just went and checked to make sure I wasn't imagining this. hahaha I smelled my sponge. Nothing. I could kind of smell the soap but nothing else. It has already lost a chunk from one edge because I've been using it so long.