Sonic Tonic

Sonic Tonic is an object that appears in the Sonic Underground television series. It is a serum created by Dr. Robotnik which grants super speed.

Description
The Sonic Tonic is a green liquid created from the essence of the Velocitree. When poured onto one’s feet, it has the power to give the user supersonic speed that can rival that of Sonic's, although a side effect of this liquid causes the user’s feet to eventually grow extremely large, preventing them from walking. This can be remedied by simply sweating out the Sonic Tonic from one’s skin.