Manager Glenn Roeder had no choice but to turn to Sinclair when Kanoute was again laid low by a heavy cold.
But on the warmest day of the season at Upton Park, England international Sinclair shone brightly in a new front-line partnership with Jermain Defoe.
Sinclair set Hammers on their way with a scorching first half strike and provided the passes for Steve Lomas and Defoe to complete the rout as West Ham turned up the heat another notch in the second half of this thoroughly entertaining game.
Hammers were well worth their 1-0 half-time lead, playing with a confident swagger and no inhibitions when it came to trying their luck from all angles and distances.
Thomas Sorensen's goal was peppered by shots from Lomas, Michael Carrick, Sebastien Schemmel and Defoe. Joe Cole, the 33,319 present and the PA announcer thought the England midfielder had given the Hammers the lead in the seventh minute when he turned in Sinclair's right wing cross from inside the six yard box, but referee Steve Bennett ruled it out for offside.
There was no denying Sinclair his fifth goal of the season, though, in the 28th minute. In a move typical of Hammers' free-flowing attacking football, Tomas Repka spread the play wide to the right touchline where Schemmel played the perfect first-time lob into space for Sinclair, who drilled a right foot volley past Sorensen from an angle eight yards out.
Apart from the occasional - and predictable - high punt aimed towards the towering Niall Quinn, the Black Cats rarely troubled David James and the back four of Ian Pearce, Repka, Christian Dailly (who had a downward header blocked on the line at the other end) and Nigel Winterburn.
Repka kept a tight grip on Kevin Phillips, collecting his 13th booking of the season for one hefty challenge from behind, while Quinn's afternoon ended early when he was replaced by substitute Kevin Kyle in the 56th minute.
That was five minutes after West Ham had doubled their advantage following a clever pass from Cole that split the Sunderland defence and allowed Sinclair to pull his cross back for Lomas to steer home his third goal of the season from 12 yards. It was just reward for the Irishman, who had gone so close with a header from a similar position at the Bobby Moore Stand end.
Sunderland's hopes of getting back into the match worsened along with their injury problems in the 68th minute, when Phillips was stretchered off with an ankle injury after a late clumsy challenge from Pearce that earned the right-back a yellow card.
With 75 minutes gone, Hammers completed an impressively comfortable victory, when the lively Lomas crossed from the right byline, Sinclair headed the ball back across goal and Defoe had the simplest of headers from three yards. It was Defoe's last touch before being replaced by Richard Garcia.
Although Thomas Butler and Claudio Reyna both went close with curling, long range efforts, Hammers should have added to their winning margin, but Cole was dispossessed as he was about to shoot, following another set-up by Lomas, while Carrick was unfortunate to see his last minute strike clawed away by Sorensen.
A 5-0 winning margin wouldn't have flattered West Ham, who outclassed Sunderland in all departments and turned on a stylish display to consolidate seventh place in the table.
And even if Kanoute doesn't rise from his sickbed in time for Highbury on Wednesday, Arsenal have been warned about Trevor Sinclair.