Sancho impressed with his performance as Dortmund beat his former club 1-0.
The Under-17 World Cup winner is missing England's U19 European Championship campaign to feature for his club in their pre-season trip to the United States.
He was supposed to travel to the International Champions cup last summer, but was left out of the team after revealing to the boss that he would not be renewing his contract with City.
He then went on to join Borussia Dortmund on deadline day for £10m, making 11 appearances in the Bundesliga this summer.
Sancho came on in the second half against City, as Dortmund made a whole team change.
He came on as the left-hand in a three man attack, putting him in direct competition with former team-mate Luke Bolton.
Sancho spent most of the game out as wide as possible, giving Bolton a difficult evening.
Although he would sometimes hold on to the ball for too long, he was able to cut through City's defence and created chances for Mahmoud Dahoud.
Sancho was also aware of his defensive duties as well , despite his obvious strength being further forward.
What did they think of Sancho's performance against City?
Sancho: "I had a point to prove and I think I did well. The manager says I need to release the ball a bit quicker. I do show off a bit sometimes, which is not that good. I need to cut that out but I will benefit from the 11 games I played last season. I have got my bearings now, so hopefully I will be better."
Lucien Favre, Dortmund manager: "Jadon Sancho is an extremely good player. You can see his talent easily. He still needs some fine tuning but he has exceptional potential."