Olivia Wilde once got ''hammered'' at work.

The 31-year-old actress, who has 18-month-old son Otis with her fiancé Jason Sudeikis, has admitted she was required to guzzle down real beer while she was shooting 'Drinking Buddies' alongside her co-stars in 2013.

Speaking on 'Off Camera With Sam Jones', she explained: ''We were hammered the entire movie because it was real beer, because beer on that set was cheaper than water, because we were shooting in a brewery.''

And it seems knocking back the booze at work soon had an effect on Olivia's co-star Anna Kendrick as she couldn't quite work out what was happening to her.

The brunette beauty said: ''She [Anna] sat down to do the first scene and took a huge gulp of beer, not realising it was real, and was like instantly hammered. She was like, 'What's happening? What are you guys doing?' and we were like, 'Oh, we forgot to tell you - the beer's all real and everyone's drunk. It's 10 am, welcome to 'Drinking Buddies.' ''

Meanwhile, this isn't the first time Olivia has addressed the behind-the-scenes shenanigans as she previously admitted they used alcohol, rather than water, to get an ''organic'' feel.

She said two years ago: ''The reason we wanted to drink the beer wasn't to loosen up, it was because we were working within this very specific world in the film, the craft-beer world of Chicago, so we wanted to to improvise accordingly.

''And this community had really adopted us, and we were working in an actual brewery. We'd have to pause scenes so a guy in a forklift could carry kegs across the floor.''