Lysol spray bottle with bleach, and plenty of hot water. Btw, I know a lot of people probably have their grow trays, etc. in places that are hard as hell to clean from. It's not like you bring down a 4 X 8 tray and just wash it in the sink. Also, going outside with it to clean it with a hose or something is most likely out of the question for many too. This is actually a more complex question than it sounds for sure.