I usually read the Hints from Heloise column in my local newspaper. It amazes me the trouble people will go to in order to save about six cents.
One frequently recurring question is, "How do I get the sour smell out of my sponge?"
Hint from Heloise:
Soak the sponge in lemon juice and rinse it out. This will remove the odor for good but keep in mind that it is important to either dispose of, bleach, or run your sponge through your dishwasher regularly to keep bacteria from growing.
Good grief. You can get a bag of sponges at the dollar store for...well...a dollar. Better yet, environment or not, killing trees or not, I never use sponges. They are filthy, disgusting bacteria hotels. I'm a paper towel girl.