The easiest solution for cleaning your key tops is the following: A Damp – not wet. If this doesn't get all the dirt and gunk off the keys then you can try a high solution of alcohol (90% rubbing alcohol) but just damp and not wet. It's important not to use too much alcohol on the keys as it can damage them.
What can I use to disinfect my piano keys?
Disinfecting Piano Keys
Dampen a cotton pad with hydrogen peroxide and use the pad to wipe down the piano keytops (back to front) between players. Use diluted alcohol-based disinfectants, do not use bleach-based disinfectants or any product containing citrus.
Does rubbing alcohol damage keyboard?
Rubbing alcohol can be safely used to clean your keyboard because it's the safest cleaning agent available for use on electronics.