In dreadful pre-season conditions, the striker's ninth minute, 20-yard volley settled the contest on an infamous, rain-soaked pitch at the Hong Kong Stadium.
City's winning margin could have been more convincing but Dzeko, who also scored in the semi-final win over South China, did not match the magnificence of his volley when sending a second-half penalty high and wretchedly wide.
It may have been a friendly tournament but the victory ensured new City boss Manuel Pellegrini earned his first trophy since succeeding Roberto Mancini earlier this summer.
It was not quite a trouble-free victory for City as key defender Matija Nastastic was stretchered off in the second half but they were the better side.
Dzeko opened the scoring early on, with Yaya Toure creating the opportunity with a flick-on intended for Pablo Zabaleta. Wes Brown got there first but the former Manchester United man could only turn the ball into the path of Dzeko, who duly rammed home a brilliant half-volley which flew in off a post.
Sunderland had a lucky escape just before the break when Craig Gardner headed David Silva's free-kick against his own post, then clattered into the upright himself as the Black Cats scrambled clear.
With heavy rain falling on an already saturated surface, an area of approximately 50 yards either side of the halfway line resembled a bog.
Dzeko was certainly looking suspiciously at it when he skied his penalty high over the bar midway through the second half.
Gardner then stopped Jesus Navas from scoring when sliding back to make a brilliant goalline clearance.