- You may be looking for the SMBZ incarnation of this transformation.
Fire Sonic is an elemental transformation that Sonic is capable of using, through the use of a Fire Flower or some other source. While powerful, this form is not actually a super form, but a Fire transformation.
Sonic the Hedgehog 2.0
Fire Sonic first appears in book/movie 7: Darth Knuckles, only in the series, he has red shoes with white cuffs, white gloves with white cuffs, and his skin turns orange, he still has red hair, and is surrounded by fire. But in his Werehog appearance, his fur is orange, his skin, and quill ends on his head are red, and his ripped cuffs are red, and his hands are still white. He only gains this form when Mark the Hedgehog enters his body. He makes a final appearance in book/movie 8: The Dark Lord, when Sonic the Werehog falls to the surface of Neptune, and lights a match when the flame (considered to be Mark) enters his body, and becomes Fire Werehog, and flies back to Mephiles, and punches him to the surface, killing him in the process.
Sonic's fur becomes red-orange, and his eyes become amber. Unlike some transformations, Sonic's gloves with become black orange-yellow cuffs, while his shoes become black with orange cuffs and soles, white stripes, and scarlet buckles.
Sonic retains all of his original abilities, while also being granted basic fire abilities granted by the transformation. Sonic is capable of abilities such as throwing fireballs, but usually focuses his powers into physical attacks such as the Homing Attack, Axe Kick, and Speed Burst. Doing so grants the attacks explosive power, and the capability of igniting enemies and objects. Sonic becomes capable of traversing over and in magma and any other heated surface or material with no injury to himself. Using his superspeed allows him to traverse rapidly moving lava and falls of such material. Using his Speed Burst power makes Sonic look like a large fireball and gives him much more power, allowing him to break through materials. In addition, Sonic is capable of using a "fire boost", allowing him to rocket into the sky or through the air.