Don't worry about germs in sponges (for most people). Wash it once in a while. We really need some germs to improve our health.
There are also studies linking sterile environment to obesity and allergies.
At this point, our entire concept of modern health/medical care is to create weaker and weaker humans, and nastier and nastier germs. We spend (USA) each year $ 3,800,000,000,000.00 (nice profitable businesses) doing it. This $ does not even include all the sanitizers we use.
I am alarmed to find sanitizer next to office building elevator up/down buttons.