Emma Watson fell ill after drinking "stagnant" water on the set of her movie Noah, after the director banned plastic bottles.
Darren Aronofsky encouraged an environmentally friendly approach which led the actress to resort to a three-month-old drink after filming an early morning scene.
The 23-year-old told Wonderland magazine: "I was so tired one morning I picked up a mug from my trailer and drank some stagnant water that had been there for the duration. I was so ill."
"Having no water bottles on set at five in the morning, when you're exhausted and delirious, wasn't ideal," she said, after everything had to be recycled or recyclable.
After the Harry Potter star, who is dating Oxford University student Matt Janney, told Darren she was "really sick," he told her to use it for the scene.