Ibrahimovic, who played Manchester United between 2016 and 2018, appeared on City's livestream ahead of the game and asked 'Do you have any viewers for this?'.
The former striker's comments prompted laughter from ex-City players Shaun Wright-Phillips and Joleon Lescott.
Ibrahimovic played for United between 2016 and 2018, scoring 29 goals for the club
Despite the huge success they have enjoyed in recent years, City have often been mocked over the size of their fanbase in comparison to some other major clubs.
While at United, Ibrahimovic played 53 games and scored 29 goals. He won the League Cup and the Europa League.
After losing 4-3 to Celtic, City were beaten again as they faced Milan despite taking the lead through Erling Haaland.
A brace from Lorenzo Colombo put Milan in front before James McAtee equalised for City in the second half.
Marco Nasti scored what proved to be the winner for Milan in the 78th minute.
City have further friendlies to come against Barcelona and Chelsea before taking on Manchester United in the Community Shield.