Sweeney was outrighted to Triple-A Buffalo on Friday, Mike Wilner of Sportsnet 590 The Fan reports.
Sweeney returned to the minors following Sunday's loss to the Tigers and is now off the 40-man roster to make room for Thomas Pannone's return from suspension. Sweeney has a .228/.309/.430 slash line with six home runs and 62 strikeouts in 158 at-bats with the Bisons this season.