Zlatan Ibrahimovic opened the scoring for United before Sebastian Larsson was dismissed for Sunderland just before the break, and Henrikh Mkhitaryan and Marcus Rashford both added goals in the second half to confirm an easy three points at the Stadium of Light.
The result also represents Sunderland's sixth defeat in seven games and they have now failed to score in 15 halves of football.
The general consensus was that Sunderland required a fast start in the North-East, but Jesse Lingard almost fired the visitors ahead on three minutes with a 25-yard strike which was saved by Jordan Pickford.
United were generally having more of the play, but they were struggling to create many clear-cut chances and that allowed Sunderland back into the contest.
Bryan Oviedo sent a weak free kick straight into the hands of Sergio Romero - a replacement for the injured David de Gea - while Lee Cattermole also had a driven effort easily saved by the goalkeeper.
However, just as Sunderland were beginning to get on top, United hit back through Lingard, who was only denied by a fine save to his left by Pickford, and a minute later, Jose Mourinho's side were ahead.
After picking up the ball on the edge of the area, Ibrahimovic held off the attentions of a defender before firing a venomous shot into the far corner of the net from 20 yards out.
United had further chances to extend their advantage through Luke Shaw, Paul Pogba and Marouane Fellaini, but Sunderland almost equalised through Victor Anichebe who held off Eric Bailly inside the penalty area before seeing his close-range flick diverted wide by Romero.
Just before the interval, Sunderland were controversially reduced to 10 men when Larsson was sent off for what was deemed a studs-up challenge on Ander Herrera, but it was the kind of decision which was left open to interpretation, rather than the call being an obvious one for the referee.
Sunderland needed to return for the second half with the first intention of avoiding conceding a second but they only held out for 45 seconds after the restart as United effectively made sure of the three points.
After receiving a pass from Shaw, Mkhitaryan bided his time in the penalty area before driving a low effort into the far corner of the net from 14 yards out.
The Black Cats initially responded well to going further behind, but it was not long before United attempted to turn the screw and put themselves out of sight.
Herrera fired over from distance before Pogba sent the ball in the same direction with a volley after being teed up by Ibrahimovic, while at the other end, Jermain Defoe directed a free kick straight at Romero.
Defoe also powered an effort over the crossbar from the edge of the box, but the majority of the closing stages belonged to United, with Mourinho introducing both Rashford and Anthony Martial.
Pogba curled a free kick marginally wide of the post, but with a minute of normal time remaining, Rashford ended his long run without a goal in the top flight.
After playing a one-two with Ibrahimovic, the young English striker sent a shot into the bottom corner from 12 yards to seal a routine win for his side and condemn Sunderland to another setback in the Premier League.