Goals from the trio secured a win for the Black Cats, moving them out of the relegation zone as the Royals remain deeply rooted in it following a disappointingly flat performance.
Sunderland got off to a fantastic start as, just two minutes in, a fairly innocuous looking corner was flapped at by Adam Federici, his miscued punch eventually falling to McClean on the edge of the box. The winger duly slammed his effort past the melee of bodies and put the home side ahead – a fine effort and a brilliant start for Martin O'Neill's side.
The lead grew after Danny Rose drove to the byline with some excellent wingplay and fired the ball across the area; Fletcher was there to back-heel the ball goalwards and put the Black Cats two ahead.
Despite the Royals attempting to assert themselves on the game, Sunderland proved too strong, and the home side almost managed to nick a third before the close of the half as Fletcher headed narrowly over from a corner.
The Royals improved in the second half, as Simon Mignolet was tested for the first time as an excellent Nicky Shorey free kick that forced him into an equally excellent save. From the ensuing corner, center back Alex Pearce headed over the bar as Reading's pressure persisted.
The away side failed to capitalize on this pressure, though, and with 20 minutes remaining, Sunderland regained control. Sessengon capped proceedings off after receiving a long ball, he rounded Federici to make it 3-0, compounding Reading's misery and securing a vital win for O'Neill's side.