The pair headed to Puerto Rico to shoot scenes for the film version of Hunter S. Thompson's novel The Rum Diary, and they intended to steer clear of drinking sessions to concentrate on work.
But the sweltering conditions left them dehydrated - and they headed to a bar to down bottles of beer just hours after filming began.
Depp tells Britain's The Sun, ""Bruce and I had made this pact initially where we weren't going to drink for the first couple of months of the film. It was to see how long we could do it for, plus we would be able to really focus on the work.
""We lasted until it was about four in the morning, about 3,000 per cent humidity and about 500 million degrees Fahrenheit and we saw this little corner 'bodega' store and I said, 'Bruce, I've got to do it'. We ran in, pounded three Coronas and that was the end of sobriety.""