Three late tries handed Batley victory in the Fleetmaster Driving Academy Heavy Woollen Derby.
The Rams led at the interval following two tries from Rob Worrincy, and Lucas Walshaw added another after the break.
But the Bulldogs were able to come from behind to seal the Roy Powell Trophy.
Head coach Neil Kelly handed debuts to a number of new signings and took the opportunity to name a large squad for the fixture.
The visitors took the lead when Jonny Campbell latched onto Dom Brambani’s speculative grubber kick, but the Rams drew level when Josh Guzdek’s cut-out pass sent in Rob Worrincy.
Both tries were goaled, and Sykes was successful for the Rams a second time following Worrincy’s interception and dash five minutes before half-time, to give Dewsbury a 12-6 lead at the interval.
The Bulldogs roared back in the opening stages of the second half when Brambani’s cross-field kick was snapped by Wayne Reittie.
But again, the host pegged their opponents back.
Sykes released Gareth Potts on the right, and the winger found James Glover, who fed Lucas Walshaw for a great score.
Sykes was wide with the goal, so it remained 16-12.
The final quarter belonged to Batley, as both head coaches rang the changes.
Tom Hemingway bounced off three would-be tacklers to score against his own club, before Joe Chandler scythed over.
The Rams saw Aaron Brown sin-binned for a high tackle, and the reduction to 12 proved pivotal in the closing stages.
Batley added the exclamation point in the final minute, when Reittie sailed over for his second try.
Dewsbury emerged from the contest with no fresh injury concerns, and will aim to make further improvements in the game against Huddersfield Giants at The John Smith’s Stadium on Sunday 14th January.