Ahh mkay, I've played this match-up from the other side (online admittedly) and it's...kinda hard for Jiggz :<
To be honest, I can't think of a strategy for Sonic to use against her. This is very much an onstage game, as there's really no point in wanting to gimp either player as if both characters are good with their respective characters, then they're only going to get gimped if they screw up horrendously.
A lot of people have suggested using usmash here. It's generally an unsafe option, thanks to the ending lag. Jiggz COULD just avoid it with her best aerial maneuverability EVAR and punish the ending lag, or if she's feeling confident try a well spaced Pound through it.
I really don't know whether you should play offensive or defensive, weaving aerials are just a problem D;
Use utilt instead of usmash, as far as I know it's less punishable as it has less ending lag.
Though, limit utilt as much as possible. I'm pretty sure Jiggz can rest you through multi-hit moves, and I'm not sure that utilt gives enough hitstun/hitboxes come out fast enough for you not to get rested through :<
Oh well, no one but me uses utilt anyways. Other multihits are safe enough. Ftilt's 2nd hitbox comes out too fast, there's no way that they're resting through usmash lol, fair I'm almost positive can't be rested through as it's a quick multi-hit, and uair's 1st hit has set knockback which puts Jiggz out of range to rest you before your second kick.
I know a footstool =>dair => rest thing was found on Jiggz's boards a while ago. If I remember, you could dair => footstool =>dair => rest? Well, it didn't say if it was affected by DI. Is it?
Keep Jiggz grounded somehow and win. Any Jiggz main worth their salt will admit that she's horrible on the ground, which is why none of them stay grounded. Keep her at range with ftilts and such. It's very much a momentum game here, whilst she's advancing it's best to play defensive/run away, whilst whilst she's retreating aerials it's always best to rush her.
Staying power and KO potential I feel is in Sonic's favour, though I have to admit that it's embarrassing dying to a dash attack. Jiggz light weight and lack of ranged KO moves ensure this (well, I know fair's good but whatever)
I see this myself as 50:50. I could see it swing 5 points in either direction though. I don't see how any side could claim an advantage without a very strong argument bringing new ideas to the table.