Marnick Vermijl and Ryan Tunnicliffe got on the scoresheet as Warren Joyce's team twice had to come from behind but qualification for the Elite phase of the competition remains in the balance despite moving into second place in the table.
The Reds suffered a pre-match blow when Davide Petrucci was forced to withdraw from the line-up and the soggy surface played its part in ensuring the first half was extremely disappointing.
Jordan Pickford had a nervous moment when spilling a Charni Ekangamene shot but he clutched it safely at the second attempt and it was the Black Cats who drew first blood on 10 minutes. Roarie Deacon cut in from the left to feed an unmarked Craig Lynch, who capitalised on the space to bury a low drive beyond Sam Johnstone.
Tunnicliffe's run led to Pickford pushing the ball away from his near post with difficulty and the keeper dealt well with Federico Macheda after the Italian displayed neat control. Adam Mitchell almost picked out Adam Reed after a Vermijl slip before United finally burst into life around the 33-minute mark.
Tom Lawrence beautifully picked out Bebe but the winger could only swerve his finish into the side-netting while, seconds later, Tunnicliffe volleyed against a post with a side-foot effort after Lawrence fed Bebe again and Macheda was unable to make a proper connection in the middle.
The second half was to provide more entertainment even though it started slowly with Michele Fornasier's important block after Deacon outstripped Frederic Veseli the only noteworthy incident until the game went goal crazy as the hour