Hey everyone! I've found a lot of Sonic SFX from various games that I thought I should share with you guys (Shadow the Hedgehog, Sonic Heroes, Sonic Adventure, Sonic Riders, etc.). Some of the SFX are not labeled and organized so you may have to go though a lot of them to find what you want. They also come with voice files from the games (particularly Sonic Adventure and Sonic Riders).
I also recorded the Sonic Spin Dash SFX from a Sonic Adventure video on YouTube but I had to use noise removal on it to remove the background noise so you may hear the "robotic sound" into it. But with your awesome mixing, you may be able to mask it.