Clean and sanitize a water cooler using a solution of 1 teaspoon of unscented bleach in a gallon of water. Unplug the cooler, remove the bottle and drain the unit before cleaning. Apply the solution with a lint-free towel and allow it to stand for three minutes.
If the water cooler has a dispenser for hot water, plug the entry from the tank into the heating unit before applying the bleach. The hot water tank is self sanitizing due to the heat. Rinse the bleach solution from the inside of the dispenser with a gallon of bottled water and repeat the rinse two more times, draining and disposing of the rinse water. Remove the hot water plug and install a new bottle of water on the cooler.