Fleet manager Liam Daish called on his side to show greater confidence in possession after the away defeat to Weymouth in midweek, and they did not disappoint.
With central midfield pairing Danny Slatter and Robert Quinn providing a solid platform in the middle, the Fleet launched the attacking talents of MacDonald and Sodje to telling effect, with both front men outstanding.
For Cambridge, defeat brings to an end a three-match unbeaten run that has been vital in keeping them clear of the relegation zone after a dismal start to the season in which they took just one point from their opening six fixtures. That the U's did not manage a single shot on target will only add to the frustration of boss Jimmy Quinn.
Gravesend began confidently, threatening early through MacDonald, who capped a strong run with a flicked shot across Paul Crichton that drifted just wide. The best chance of the opening quarter fell to Quinn, who tested Crichton's handling with a stinging shot from the edge of the area.
That moment seemed to spark Cambridge into life, Ritchie Hanlon delivering a beautifully-judged through ball to release Liam Marum, who drew a brave smothering save from Fleet goalkeeper Lance Cronin.
Marum continued to threaten sporadically in tandem with strike partner Marcus Richardson but, with Cambridge struggling in the possession stakes, Gravesend continued to look the likelier to make the breakthrough.
MacDonald's bustling runs down the inside-right channel were causing U's left-back Trevor Robinson and his defensive colleagues all manner of problems.
After capitalising on a defensive error to test Crichton with a firm shot from just inside the area, the lively 25-year-old chested down a Mark Ricketts cross superbly only to fire straight at the Cambridge goalkeeper.
However, as against Dagenham & Redbridge in their last home outing, the Fleet were struggling to translate territorial advantage into goals, and with Michael Morrison and Matthew Bloomer strong and resolute at the heart of the visitors' defence, Cambridge made it through to the break all square.
The visitors re-emerged in marginally more enterprising vein, but were almost caught out when Slatter found Sodje with a defence-splitting pass. Clean through, the Nigerian-born front man skewed his shot just wide of the scrambling Crichton's upright.
Had Cambridge not had a goal disallowed for offside when Richardson beat Cronin with a diving header a few minutes later, Sodje's miss might have proved costly.
As it was, the Fleet responded vigorously, Sodje redoubling his efforts and Slatter firing in a long-range effort after the ball broke to him on the edge of the area.
With 20 minutes to go, the Fleet's pressure finally paid off. A testing first half at the hands of MacDonald had clearly addled the mind of Robinson, for as Slatter delivered a corner into the six-yard box, and Moore's shot arrowed towards goal, the Cambridge defender diverted the ball on to the post with his hand to earn a straight red card. MacDonald converted the penalty for his 11th goal of the season.
If that was just reward for MacDonald after a fine performance, but Sodje was not about to let his strike partner outshine him. Minutes later he latched on to a precise pass from Slatter, shrugged off a poor first touch and drove past Crichton to send the Stonebridge Road faithful into delirium.
Cambridge could have had a late consolation goal when substitute Courtney Pitt squared for Richardson, but somehow the Cambridge front man contrived to miss and it was Gravesend's afternoon.