"Hathaway, get this. This is a f–king real challenge," said Stewart, 24, who was given the challenge by her pal Anne Hathaway. "In good faith you must believe this was all done with dirty bath water. Please be considerate of California water conservation."
The Twilight alum and Hoult, 24, dunked their heads in blue buckets for as long as they possibly could. Afterward, Jennifer Lawrence's ex and Fahrendorf (who's previously worked as a crew member on Stewart's films On the Road and Camp X-Ray) grabbed a bigger bucket to drench the actress. The stars are currently filming Autobahn in Germany.
Just like others who've accepted the dare, Stewart and Hoult then nominated some of their famous pals to follow suit.
Watch the video now and find out who they chose! (Warning: F-bomb alert!)
For access to all our exclusive celebrity videos and interviews – Subscribe on Youtube!