when you or someone farts around a person drinking water. the water is automatically considered fart water. this is because water evaporates and also gets tainted by the air. the water is usually not always no less good.
*person A farts and contaminates the surrounding air with their gas*
*person B takes a drink of water with their mouth wide open*
*person A says: "haha you just drank fart water!! HAHAHA"*
*person B swallows carelessly"