I've heard you can clean sponges by putting them in the dishwasher or microwave. Is that true?

Sponge is better to be disposed after use.

For cleaning procedure of sponge in case of re-use in case of need:Boiling in immersing water for half an hour to kill all microorganizms, cooking food debris and solving all fats.

Foaming to clean up any particles and rinse in fresh water (temperature and time factors are controlled by dish-washer.

The same procedures are applied for the table towels in the same case.

After all these precautions the sponge will be used under risk parameters for urgent cases.