Like other water containers, a bleach bottle with water will automatically satiate the player's thirst. Therefore, a bleach bottle with water will gradually lose its contents, and need to be refilled, being replaced with an empty bleach bottle.
Its main purpose is to store water. This can be done by pouring out the contents of a bleach bottle (or drinking) and refilling it from a water source.
Empty bleach bottles can be found sitting on corpses, suggesting that the Knox Event drove them to suicide.
Naturally spawning suicide victim
Bleach Bottle with Water From items_food.txt (Project Zomboid directory/media/scripts/)