rubbing alchohol and salt does the trick...don't use cleaning products. You can use really hot or boiling water to get some gunk out and then in a separate container mix some regular rubbing alcohol and some non iodized salt (you can use vodka and regular salt too sometimes..) and then shake vigorously..but be careful obviously. If it's really dirty you can soak it for a bit first with hot water (that loosens the grime) and then use the alcohol-salt mix to clean it.