Michael Parkhurst sent a long ball to Federico Higuain, who forced goalkeeper Tim Melia to make a diving save that deflected to McInerney. The open tap-in was McInerney's 37th career goal. He is the second youngest MLS player (23) to reach that mark behind the Crew's Stern John (1998-99).
Tony Tchani tied it for the Crew (10-8-8) in the 80th minute, finishing Tyson Wahl's glancing header.
Graham Zusi gave Sporting (11-6-7) a 2-1 lead in the 62nd minute with a right-footed blast from the top left corner of the 18-yard box.
Marcel de Jong opened the scoring in the 14th minute for Sporting and Ethan Finlay answered for the Crew in the 35th minute.