When the player is on fire and he drinks from the bottle he will automatically extinguish himself instead of drinking. However it depends on how much the bottle is filled. When the bottle is full and the player extinguishes himself the bottle will be emty but when the bottle is half full it won`t extinguish the player but it will reduce the burning to half. It depends on how much water is inside, it will then reduce the amount of time your burning.

Nice idea, thank you!