Michael McNicholas and Liam Coughlin each had a goal and an assist for the Vipers (1-1-0), who led 5-1 heading into the second intermission after scoring three goals in 41 seconds to open the middle period.
Dylan Johnson, Tyson Enzie, Brett Boehm and Tanner Lischynsky scored for the Terriers (0-2-0), who cut Vernon's lead in the third period to 5-4 before Sparrow capped the win with his third goal of the game at 19:17.
Austin Smith made 40 saves for the Vipers. Kale Thomson started in net for Yorkton but was pulled after allowing five goals on 18 shots. Riley Medves stopped 14-of-15 shots in 36:12 of relief.
Vernon went 1 for 4 on the power play while the Terriers scored twice on eight chances with the man advantage.
Preliminary round action continues on Tuesday with two games on schedule. The Toronto Lakeshore Patriots (1-1-0) will play the Carleton Place Canadians (1-1-0) while the Vipers face the Dauphin Kings (2-0-0).