Chelsea sent out a message with a thumping 7-0 win against Norwich City earlier in the day, but City responded with a convincing win of its own to close the gap on the leader to two points.
Foden's double at Amex Stadium came after Ilkay Gundogan had opened the scoring as the visitors went three goals ahead inside 31 minutes in a dominant first-half showing.
Brighton improved in the second half and pulled back a deserved consolation nine minutes from time through substitute Alexis Mac Allister's penalty, but City had the final say when Foden played in Riyad Mahrez for a late fourth.
Lewis Dunk produced an acrobatic goal-line clearance to deny Gabriel Jesus early on, but Gundogan tapped in two minutes later after Robert Sanchez failed to take a routine catch and Bernardo Silva hooked the ball into his City team-mate's path.
Sanchez initially did well to keep the scoring down with a couple of good saves, only for Foden, who was under pressure from Brighton defender Dan Burn, to double his side's tally by converting Jack Grealish's unselfish pass at the end of a swift counter.
Foden was credited with the goal after some initial uncertainty over whether he or Burn got the final touch, and he had a second soon after, the England international getting in the way of a Jesus shot to help deflect it past a wrong-footed Sanchez.
Brighton recovered from two goals down to beat City 3-2 at this ground in May and they grew into the game in the second half, with Pascal Gross and Leandro Trossard finally calling Ederson into action.
City could not hold on for a seventh clean sheet in nine league games this term as Ederson caught Enock Mwepu and fellow Albion substitute Mac Allister made no mistake from the penalty spot, but there was still time for Mahrez to lash in his seventh of the season at the other end when played in by Foden.
Both sides are in Carabao Cup Round of 16 action on Thursday (AEDT), with City travelling to West Ham United and Brighton away to Leicester City.