Kevin De Bruyne made his return to the Manchester City side as the FA Cup holders began their defence by thrashing Huddersfield.
Fielding a strong side, City suffered a setback when they lost defender Manuel Akanji to injury early in the first half, but Foden's superb finishing and De Bruyne's comeback gave coach Pep Guardiola plenty to be happy about.
Huddersfield, who are hovering just above the relegation zone in England's second-tier Championship, fell behind in the 33rd minute when Foden rifled the ball into the net from a tight angle, and striker Julian Alvarez poked home a second four minutes later.
De Bruyne entered the fray in the 57th minute and City added their third a minute later as Norwegian winger Oscar Bobb tried to pick out the Belgian at the far post, only to see his deflected cross loop into the net to make it 3-0.
Foden added his second with a precise shot from the edge of the area in the 65th minute, and nine minutes later De Bruyne teed up fellow substitute Jeremy Doku to complete the rout.
Elsewhere, City's Premier League rivals Luton Town were held to a scoreless draw by Bolton Wanderers, and Nottingham Forest and West Ham United will also need replays after draws with Blackpool and Bristol City respectively.
