You can't sterilze headphones, but you can disinfect them. Several disinfectants on the market will do nicely. Heck, Lysol is pretty solid in that regard. Best to spray it on a clean cloth and wipe things down. You don't want to get into the drivers with it. As for the pads, if you're really worried about them, simply buy a new set. Be aware that long term/repeated use of alcohol will dry out most materials. It will also lead to cracking and peeling of the surface finish on most headphones. We've gotten away from alcohol based disinfectants in my business due to that very problem. As I said, it will get to rubber, plastics, vinyl, leather, etc....if you use it long enough, eventually it will happen.
Bottom line, Lysol wipe and buy new pads. Btw, for alcohol to "sterilize" it would have to be in direct contact with the surface for at least 30 minutes, but I just don't recommend "headphone dipping/bath".