|This object exists primarily or exclusively within the Sonic Underground continuity.|
Information in this article may not be canonical to the storyline of the games or any other Sonic continuity.
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.