The Sharks trailed by just three points at half time but saw the game rapidly slip away from them in the third quarter and trailed 75-56 by the end of it.
And the Giants maintained their impressive scoring efforts to secure a 101-72 triumph at the final buzzer.
Sheffield missed the opportunity to cut the gap to BBL Championship leaders London Lions to two points and put further daylight between themselves and the chasing pack.
Manchester got off to the stronger start but an 8-0 run pushed the Sharks into the lead, which they held through the remainder of the first period which finished 21-19.
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The Giants pushed ahead early in the second but the Sharks rallied again, cutting the deficit to one via a three pointer from skipper Mike Tuck.
Manchester again ticked ahead and looked set to carry a healthy lead into half time only for Williams to take his tally to 21 and leave the Sharks three points behind.
However Sheffield simply could not match the scoring efforts of their visitors in the second half and they pushed into a double digit lead for the first time in the game before finishing the third quarter with a 19 point advantage.
Such comfort would never be relinquished and at the buzzer Manchester held a 29 point lead to emphasise their dominance on the scoring front.
Alexander's 26 point haul as the game's best but the Giants were scoring from all across the side with six men reaching double figures.
Mike McCall Jr and Torry Butler both landed 22 points for the visitors with Ingus Bankevics and Vlatko Granic supporting with 17 apiece.
The Sharks remain at home for their next fixture on Friday when they host defending champions Leicester Riders.
The Riders trail second placed Sheffield by eight points but have six games in hand.