Despite what many think, the cause of Sonic.exe's yellow teeth is one of the few side effects when his body was made. However, the blood on his mouth strongly implies that he eats the remains of his victims after taking their souls.
Sonic.exe is a horror game, it is based on a creepy story about a person who played a haunted version of Sonic The Hedgehog. It is graphic in nature, includes scenes that are bloody and is designed to generate jump scares. Some children will be disturbed by it.