The green energy fluid is a volatile form of green liquid energy. In gameplay, it is harmful to the (unprotected) playable characters, causing damage upon contact.
Sonic Adventure 2
The Green energy fluid, though unnamed, first debuted in Sonic Adventure 2, and later appeared in its enhanced port Sonic Adventure 2: Battle. It appears most notably in Cannon's Core, appearing in all of the character's sections aside from Tails and Sonic's.
Shadow the Hedgehog
In Shadow the Hedgehog, green energy fluid is exclusively found in the Space Colony ARK stages, such as Space Gadget. The player can traverse this liquid without getting harmed by it using an Air Saucer. Alternatively, the player can walk across the liquid using the invulnerability grated by the Hero or Dark Shadow state.