The girls sang along to a karaoke version of the tune on a big screen at the Texas press conference in response to a question asking if they were lip-syncing to another Britney number in the film, reports British newspaper The Mirror.
Vanessa Hudgens and James Franco also co-star in the movie about a group of college girls who get into hot water after going on a crime spree to fund their spring break.
The adult drama is a deliberate departure for Gomez, who acknowledges she has a young fan base.
"I was getting kind of repetitive in terms of the roles I was picking, and I really wanted to do something that was completely different," she recently told Interview magazine.
"I want to be taking myself seriously as an actress, and this was definitely a stretch.
"I mean, I'd never smoked a cigarette before in my entire life. It was really funny - they had to show me how to do it."
- Cover Media
