A common stone? Really? Any context behind why Superman passed out over a stone?
He was trapped inside one of Brainiac's bottled cities, where he was stripped of Earth's yellow solar radiation and completely depowered.
Unlike Sonic or Flash, his power is connected to the sun.

So technically Sonic, Shadow and Knuckles aren't in Fortnite, but robots of Fortnite size are?
Seems a bit of a cop-out.
It's the easiest way to answer the investors if they ever ask
"I saw a picture of our kid friendly mascot Sonic the Hedgehog's using a gun. How could you let that happened?"
"No, Sir. That's not Sonic. That's Sonic Robot."
"Ah, make sense. Carry on."