Lily James "sucked on pennies" to mask her teenage drunkenness.
The 'Pride and Prejudice and Zombies' actress got caught up in "naughty" behaviour when she was at a performing arts boarding school, such as buying alcohol in the local village at weekends, but went to great lengths to conceal the fact she was intoxicated.
She told Town & Country magazine: "Matron started breathalysing us, so we'd suck on pennies to neutralise our mouths."
In 2014, a string of celebrities, including Lily's boyfriend Matt Smith - who was dating Daisy Lowe at the time - had their private photos hacked and the 'Cinderella' star admitted the "terrifying" incident has caused her to "censor" herself more.
She said: "It was terrifying and so unfair.
"It makes you conscious of not doing... You shouldn't have to censor yourself in that way. I've begun to think like this, and it's really sad."
When it comes to her salary, the 26-year-old star suggested she hadn't been treated fairly as people have "taken advantage" of her.
Discussing Jennifer Lawrence's outspoken stance on the gender pay gap, Lily said: "I realised really early on, especially because I'm young, that people will take advantage.
"I'm very open, and I stupidly thought that people would be open and fair with me, but they're not. I sort of found out the hard way."