The Bundesliga side took a shock lead at the Etihad, with Andrej Kramaric tucking home from the penalty spot after Aymeric Laporte had been adjudged to have pulled beck Banjamin Hubner.
With all the talent at city's disposal, though, it always felt like it was just a matter of time before they drew level and so it proved as Sane took centre stage on the stroke of half-time.
The German took responsibility over a free-kick 25 yards out and duly curled it over the wall and into Oliver Baumann's top left-hand corner.
The Hoffenheim stopper was left a mere spectator and there was little he could do on the hour mark either as Sane completed the turn around.
The winger started a counter, exchanging passes with Raheem Sterling before drawing Baumann off his line and changing the angle of the strike at the last minute to slot home his second of the night.