Sonic Frontiers is ready for launch on November 8, 2022 and it looks like you can receive a DLC code to receive Sonic’s Soap shoes from Sonic Adventure 2 in Frontiers. All you have to do is sign up to the newsletter that is on the official website for the game.
— Wario64 (@Wario64) October 3, 2022
This is a not only a unique way to get free in-game content, but to get people to sign up for a newsletter.
Recently the opening cinematic and Super Sonic boss fight was leaked for Sonic Frontiers.