Sonic - I can't camp him or approach him, he controls the whole fight and I definitely can't ever punish him, always get grabbed and turnips always feel like a loss for me anytime I even remotely think of grabbing one. Serious business this Sonic is, plus I get grabbed a LOT. I failed cause I died by his predictable F-Smash I guess.
You don't need to approach him. Sonic has pretty much zero approach options, since he's got no projectiles or horribly disjointed moves. If a move is coming his way, chances are he has to shield. Provided you get a few hits on him and just sit there, he can't do a right lot. At the end of the day, Sonic will always have to commit an approach and essentially you can just move out of the way of his moves and punish them with a Bair or Floating aerial. Turnips aren't as effective as they are in other match ups because Sonic is simply too fast for you get them up safely most of the time
You might find yourself getting grabbed by Sonic because by the time you've come down to use an aerial, he's already run up to you causing you to mis space an aerial. Don't be afraid to throw a few random Fairs out - since there's no lag, there's nothing for Sonic to really punish you for. If the Fair doesn't hit, no biggie. Get Dairs on his shield if you can, his Up Tilt is very slow and not very good, his Up Smash is slow and his Up + B won't do any damage to you
A lot of (bad) Sonic's instinctivly Up + B and Dair when they feel in danger. Just stay on the ground, avoid the Spring and punish Sonic as he's coming down from the Dair. A Floating Nair is probably the best move to use since you can move and the hitbox will last long enough for you to catch him in those few frames of landing. Speaking of Floating Nairs, use them. Nair will outprioritize Sonic's spindashes so if he spindashes into you, Nair him
When recovering, be very wary of what Sonic is going to do. Don't be tempted to come crashing in with a Fair when recovering, an up angled F Smash from Sonic would send you flying. If you get hit up in the air or Sonic Up Throws you, watch they don't Spirng to Uair. Either move out the way or if you're feeling plucky, use Dair and hope they actually get killed by the final hit xD
At a glance Sonic has very good recovery but tbh if you ask me its not as great as it looks. His Up + B doesn't auto snap to the ledge and has a wierd tumble so you can gimp by grabbing him but most Sonic's will never put themselves in a situation to let that happen. If Sonic recovers low, you can sometimes get an Up Smash on him when he's springing up.
Sonic is one of the only match ups I'm actually confident about giving advice for and probably the best thing you can do is to play him at his own game. Sonic is mainly about punishment and captalizing on your mistakes. Peach can do exactly the same to him, only better