I like to use Sonic's mobility to my advantage for mind games, like I'll bait opponents to chase after me if I can, run in one direction, immeadiately spin dash in the other for a quick set up, if I want to get in I'll either use his forward air after a short hop or side special which I use most often because the fact that you can jump cancel that is good for fake-outs. One particular fake-out I like to do is side special + jump cancel backwards + down special while I still have air time + jump cancel forward + get in with either a dive kick, homing attack, side special or down special.
I'm also comfortable enough with Sonic that I'll use the spring in crafty ways, like timing it just right over an edge for edgehogging or using it as another fake out tool by using it just as you're about to land near the opponent, it's not a method people see often so you're likely to successfully have the spring deal some damage, it's not big damage mind you but it's good for throwing the opponent off guard.
And finally since Sonic has trouble getting kills, I like to use Sonic's air game and recovery to take some pretty nasty risks I'll admit so if I've knocked my opponent off the field, I'm going to try what I can to force them off screen by meeting them in the middle of their recovery.