Home tips you can try:
Microwave the wet sponge:
Microwaving your sponge can kill 99 percent of the bacteria that cause it to smell. Place a dampened sponge in the microwave on high for 1 to 2 minutes to kill rapidly colonizing bacteria, molds and yeast. Never microwave a dry sponge, it could ignite. And do not microwave any sponge with metallic fibers for scrubbing. Once the germs are fried, let the sponge cool off before grabbing it so you don’t burn your hand.
(Note: don’t microwave a dry sponge – fire hazard)
Soak in vinegar, lemon juice or bleach and then soak in a mixture of baking soda and water:
Soak the entire sponge in acidic liquids like full-strength white vinegar or lemon juice to kill bacteria, mold, yeast and viruses. You can also soak the sponge for one minute in a solution of 1/2 teaspoon bleach in 1 quart of warm water. But this won’t get rid of all the undesirable bacteria as well as the microwave
Put the sponge in the dishwasher or hot water:
Another way to wash your sponge is the dishwasher. Place it into the dishwasher for the entire cycle, wedging it securely in the top shelf so it stays put while it is washed, rinsed and most importantly blasted with heat to dry. Water that is 140 degrees Fahrenheit or higher will kill the germs hiding in your sponge. Use two sponges, and rotate them out between dishwashing cycles
We have tried all of these suggestions and none of them do the job for good.
The microwave has been noted to kill some of the dangerous bacteria, like salmonella and E.Coli, but in our experience the smell remains or comes back very quickly.
The vinegar and baking soda trick works for about half a day, but eventually the smell comes back.