The hosts took the lead in the 34th minute when striker Keinan Davis was presented with a tap-in after Hassane Kamara’s low cross.
Defender Aji Alese then drew Tony Mowbray’s side level on the stroke of half-time after his effort sneaked over the line.
Watford started strongly in the second half and retook the lead when Luke O’Nien headed the ball into his own net, yet Black Cats substitute Jewison Bennette scored a dramatic equaliser three minutes from time.
Our Sunderland writer Phil Smith has dished out his player ratings from Vicarage Road:
5. Aji Alese - 8
Played an important part in trying to get Sunderland up the pitch by overlapping Clarke and was rewarded for another excellent display with his first goal. Cramped up towards the end which underlined the effort he’d put into it. He’s had a superb week. Player of the match. 8 Photo: Frank Reid
6. Corry Evans - 6
Understandably tired in the second half after doing well in the first. Ba made a terrific first impression in his place late on, which is a boost. 6 Photo: Frank Reid
7. Dan Neil - 6
Tidy on the ball throughout and competed well but was one of many who were obviously tiring as the second progressed. 6 Photo: Martin Swinney
8. Elliot Embleton - 5
Had one or two bright moments on the ball through the first half but was one of many who struggled to impose himself on the second. Withdrawn after the second goal as Sunderland tried to get a threat in behind the Watford defence. 5 Photo: Frank Reid