Senior Film and Media Reporter

Dakota Johnson was feeling a little nervous while filming "Loser Baby," a short film that serves as her directorial debut and is premiering at the Toronto International Film Festival. But it wasn't nerves that had her on edge.

"I discovered Celsius on day one of filming," she said in the studio at Variety's Toronto Film Festival, sponsored by J. Crew and SharkNinja. "I didn't know it was like Red Bull. I thought it was a natural drink."

At first, she attributed the energy boost to being in the zone. "I thought, 'I'm so creative. I'm so inspired. I'm up all night. I don't sleep because I'm just thinking…'" Johnson recalls. "And that's because I was getting two degrees Celsius a day. I thought it was vitamins. I didn't realize I was actually overdosing on caffeine."