Alan Gow, fellow striker Ashley Barnes and midfielder Luke Summerfield were also on target for Argyle, who tested a 3-4-3 formation.
Manager Paul Sturrock was present to watch the game, in which fit-again defender David McNamee made his comeback, proving his fitness ahead of Saturday's Championship trip to West Brom.
Sturrock said: "The attitude of the players was fantastic from the first whistle. We were up against very strong opposition which made it even more pleasing."
City's side included Holland Under-21 midfielder Evander Sno, making his first start since joining them on loan from Ajax.