Nightcap (drink)
A nightcap is a drink taken shortly before bedtime. For example, a small alcoholic drink or glass of warm milk can supposedly promote a good night's sleep. Alcoholic nightcaps and sleep. Traditional nightcaps include brandy, bourbon, and cream-based liqueurs such as Irish cream. Wine and beer can also function as nightcaps. In folk medicine, consuming a nightcap is for the purpose of inducing sleep. Alcohol is not recommended by many doctors as a sleep aid because it may interfere with sleep quality. But, in low doses, alcohol has sleep-promoting benefits, and some popular sleep medicines  include 10% alcohol, although the effects of alcohol upon sleep can wear off somewhat after several nights of consecutive use. Non-alcoholic. A nightcap was originally alcoholic, since it makes the drinker feel warm and helps them sleep, just like the garment of the same name. However, warm milk is often recommended as a nightcap for inducing sleep. It contains both tryptophan and calcium, which both help induce sleep. The flavor of the warm milk can be improved by adding a small amount of liqueur or vanilla extract, which contains ~45% alcohol, which may promote sleep as well. Alternatively, honey  can improve the flavor. The effectiveness of warm milk for inducing sleep is disputed. In 1930, Ovaltine was advertised as "the world's best 'night-cap' to ensure sound, natural sleep".