Acid Vial (cos).

As an action, you can splash the contents of this flask onto a creature within 5 feet of you or throw it up to 20 feet, shattering it on impact. In the case of throwing it, make a ranged attack with an improvised weapon, in the case of a target within 5 ft, the target must make a Dexterity saving throw equal to the wielder's weapon DC (Dexterity). On a hit, or a  failed save, the target takes 2d6 acid damage. If given 1 minute of time a vial of acid can corrode one cubic inch of non-magical metal or ten cubic inches of nonmagical wood. A vial of acid can corrode up to 30 cubic inches of material.