I imagine this playing in a Modern Sonic stage where Sonic would have not gained his full strength back from being trapped on the Death Egg for so long, so much he needs to escape robots chasing him down through this familiar city. (Or he could be running away from Infinite and the villains trying to re-contain him.) Infinite would use the Phantom Ruby to summon the G.U.N. truck, specifically from the modern generations stage. The stage instead ends with Sonic entering a manhole cover to hide from the villains/robots.