What is a "nightcap" drink?

A nightcap is an alcoholic beverage consumed at the end of the day to help people sleep. It's usually a strong drink, such as a liqueur or liquor.

Traditional drinks of choice are brandy, bourbon or Irish cream, but wine and beer are popular as well. Nightcaps often disrupt sleep or diminish the quality of sleep a person gets. According to a study by Williams and Salamy published in the 1970s, although the alcohol may help people fall asleep faster and remain asleep for the first part of the night, those people tend to wake up during the middle of the night. This is described as a rebound effect.