United hit back from a goal down to build up a 3-1 lead with Sunderland's late strike no more than a consolation.
Reserve manager Tommy Craig: "It was a hard-earned win on a quagmire of a pitch but the main thing is we got through it. I was pleased with the way we came back from a goal down so early. We have done that in the last two games but we showed resilience once again and went in search of the equaliser.
"There were a lot of good hard working performances. Overall I thought we were worth more goals but we needed to be more clinical."
Tommy Miller's low shot from just outside the box clipped off Toon defender David Edgar and past Steve Harper to put Sunderland ahead.
Carl Finnigan's diving header flew past Joe Murphy from an Alan O'Brien left wing cross on 37 minutes before Edgar nodded home from another O'Brien cross two minutes later after Daryl Smylie's effort had bounced off the bar.
When O'Brien's corner was knocked into Smylie's path by skipper Kris Gate, the Ulsterman scored past Murphy to make it 3-1.
Sunderland's French striker Anthony Le Tallec broke free and beat Harper with 10 minutes left. Sunderland's Christian Bassila was sent off for a foul on Carl Finnigan with two minutes left.
NEWCASTLE UNITED: Harper, Baxter, Cave (Atkin 90), Edgar, Huntington, Farman (Carroll 31), Brittain (Marshall 62), Gate, O'Brien, Finnigan, Smylie. Subs (not used): Cook, Shanks
SUNDERLAND: Murphy, Taylor, Collins, Christensen, Smith (Allan 72), Graham (Hartley 54), Bassila, Miller, Le Tallec, Murphy, Dennehy (Smith 69). Subs (not used): Trevor Carson, Jay Martin