There were rare appearances for goalkeeper Zack Steffen, Nathan Ake, Gabriel Jesus and Cole Palmer as Pep Guardiola rang the changes after the win over Arsenal.
Swindon struggled to contain their counterparts and trailed on 14 minutes when Bernardo Silva tapped into an empty net from close-range following a low cross by Palmer.
City caught the host in their wake before the closing quarter of the first half after a high-press scenario saw Kevin De Bruyne play a first-time pass to Jesus, who took aim and finished with ease.
A third goal nearly followed a minute to halftime courtesy of Joao Cancelo's thumping strike outside the area, but he instead battered the outside than the inside of the net.
The one-way traffic continued in the second half, as City snatched a third after Ilkay Gundogan's low free-kick from outside the area curled beyond the wall and into the net.
The Citizens could've made it four after a five minute spell, but Jesus had his spot-kick saved by the Swindon shot-stopper after he had gone down in the area.
Swindon threw themselves a lifeline in the last 12 minutes as Harry McKirdy opened space on the far side to go on and beat Steffen with a stern finish.
However, City restored their advantage after a few minutes when Palmer cut an opening from a tight angle and curled in off the crossbar.
More goals looked on the cards for the Citizens through Rodri's first-time effort outside the area a minute from time, but he hit the underside of the crossbar as the Citizens marched on to a comfortable victory though.