A much tougher test will lie ahead in the last eight as Sporting set out at the Etihad just to avoid another embarrassing scoreline like the one they suffered on home soil.
Guardiola handed a European debut to teenage right-back CJ Egan-Riley with a number of defenders out through injury, illness or suspension.
Rodri, Kevin De Bruyne and Riyad Mahrez were also rested from the start, but City should still have won the game comfortably.
Raheem Sterling wasted the best of the home side's chances as the England international failed to lift the ball over Antonio Adan from Phil Foden's sensational through ball.
After an uneventful first half, City thought they had claimed the lead through Gabriel Jesus early in the second period.
Mahrez, introduced at the break, ran into the box and slid the ball into the Brazilian on the left.
Jesus smashed in from a tight angle but the goal was disallowed for offside following a VAR review.
The state of the tie was summed up when Guardiola took the chance to give Carson his first Champions League appearance since 2005, replacing Ederson 17 minutes from time.
Carson was called into action to bravely block from Pedro Porro with Sporting's best chance moments later.
Mahrez, John Stones and Sterling all missed chances late on to break the deadlock, but Sporting salvaged some pride by holding out for a clean sheet.