What religion is Sonic the Hedgehog?

Answer 1

Most likely athiest, or another which is laid back. The easiest thing to do is to eliminate what religions he can't be.

Buddhist. Although Sonic lives a life without many material objects, he doesn't really try to eliminate suffering. For instance, he happily taunts Metal Sonic at the end of Sonic Heroes. Metal may be an animal which has been imprisoned in a robot, like many designs of that era. He also killed the Biolizard.

Christian. Probably not, as he lies to Eggman about the fake chaos emerald in Sonic Adventure 2. There is a church in Sonic Unleashed, so Christianity probably exists in his world.

Jew. In Sonic Unleashed, he eats a variety of non-kosher foods, like pork (in chili dogs). Or at least not a kosher Jew.

Muslim See above. Pork is banned in Islam. We see a Mosque in Sonic Adventure 2, so it's possible that Islam exists in Sonic's world too.

The chances are, after battling three gods (Chaos, Solaris and Gaia), Sonic is just willing to accept whatever life throws at him.