Orlando City's star player Kaka scored the only goal of the game during the 29th minute of play.
Afterward, both teams took a rare break to rehydrate.
MLS rules mandate the water timeouts this season during high heat and humid games.
The clock didn't stop, but the short break was accounted for after the normal 90 minutes of play.
It's the third time the Orlando City Soccer Club has played against D.C. United.
In the first two games, Orlando City lost, making the third game a big victory for the team.
Sunday's game drew a crowd of 30,054 fans, according to the Lions.
The Orlando City Soccer Club will face off against the Charleston Battery on Wednesday at Blackbaud Stadium.