A water toadie egg antidote is the cure for a water toadie egg, which causes the eater to have green skin. The antidote is a yellow liquid that tasted like soda pop and cabbage. Jake Grimm had it in a glass vial with a cork stopper.
We know that this is a magical item because after Sabrina Grimm consumed it her father muttered "Magic," with disgust, because it had a side effect.
Once the antidote is drank, the consumers skin instantly changes to its normal hue. However, a side effect is that the drinker grows a monkey's tail, sometimes instantly or within a few days.