She spends like a drunken sailor
SO said this to me while we were discussing family financial situations. He was talking about how his wife tends to spend extravagantly with little thought and said that, she spends like a drunken sailor.
He did not remember first hearing this metaphor from any one person, but claims that it is said often enough that he has picked it up. He believes that the idea of spending like a drunken sailor, stems from a particularly bad aspect of sailor behavior. He explained that sailors are often out at sea for long periods of time, cooped up on a small boat without a lot of communication or luxury items. When they land in port, there is a general belief from the public that these sailors will go a bit crazy with all the freedom they suddenly have. These sailors will take advantage of their access to alcohol, food and women, spending all their money on a few days of extravagance.
The use of this particular metaphor reveals the variation that is common in telling folklore. SO was referring specifically to his wife and her spending habits, consequently, he said, she spends like a drunken sailor. However, other words could be put into the place of she in order to say that he, they, you, or a specific name, spends like a drunken sailor. The phrase can be modified easily to fit a wide range of people and situations.