Imagine this set-up in a comedy film: two men are trapped under a sewer because of some freak accident. It was just coincidence that the other character in the story has a flask with him. As the scene goes on, the two tough characters began to tell each other their life stories taking turns at a swig from the flask. After sometime, the alcoholic beverage in the flask begins to kick-in that as they go on with their stories, one of them begins to break-out and cry, which is a really funny scene.
That movie is I-Spy starring Eddie Murphy and Owen Wilson. In the movie, the flask is subliminally guiding the attention of the movie-goers, while it can also act as a cue for the actor that he is about to speak his script lines. Flasks make great props in movie scenes where there is a conversation between two or three actors. This strategy has been used a number of times in Hollywood films.
Off reel, flasks, especially hip flasks, were restricted to gentlemen or people with noble birth during the old days, although, it is not so surprising to discover women with tucked flasks in their garter belts as well. It is always filled with liquor and is supposed to keep the body...