The 2018 and 2019 champions started the season sluggishly but have hit the accelerator in recent weeks and are now just one point behind Liverpool with a game in hand.
City's relief at finally breaking through was evident, although amid renewed calls for players to curb goal celebrations, the large group hug that formed may attract scrutiny.
De Bruyne tested Sanchez again with a powerful shot following a corner and the Belgian also had a free-kick blocked after Adam Webster was deemed to have passed back to his keeper.
On Sunday, the 26-year-old was introduced as a second-half substitute as Brighton defeated League Two club Newport County on penalties in the FA Cup.
England global Foden took his tally for the season to eight goals in all competitions at the Etihad Stadium on Wednesday, making him City's highest-scoring player in 2020-21.
Riyad Mahrez should have doubled the lead in the 58th minute, sending his left-footed shot wide after being put through.
Brighton, tidy in possession and solid at the back, were close to reaching the interval on level terms but were undone by a superb City goal.
Mahrez was unable to supply the finish at the end of an intricate move around the visitors' box, before De Bruyne was again denied by Sanchez following a counter-attack from Brighton's first corner.
"We had a really good first half and had chances".
Brighton engineered some promising situations but failed to properly test Ederson.
The win means City are now unbeaten in their 14 games in all competitions and have won seven in a row.
City should have killed off the game in injury time as Sanchez brought down De Bruyne but substitute Sterling blazed over from the spot.
Guardiola's team have largely brushed off the absences of a number of players as a result of various coronavirus issues.