Sydney Sweeney got high at Stagecoach ... and, we mean that literally -- because Scooter Braun lifted her into the air on his shoulders. Video is circulating online of the TV and movie star hopping on her man's broad shoulders for a lift during the festival. Check it out ... these two are clearly couple goals -- with Braun standing firm while Sweeney sang her heart out to an Ella Langley song. They've clearly got security ... but, no one is trying to bother the pair as they bounce along to the