Drinking an alcoholic beverage that contains impurities or preservatives can give you a hangover, even if you only have one drink. Some of these impurities may be other alcohols besides ethanol. Other hangover-causing chemicals are congeners, which are by-products of the fermentation process (Fermentation, in simple terms, is the chemical conversion of sugars into ethanol.). Sometimes impurities such as zinc or other metals may be added to sweeten or enhance the flavour of liqueurs. Otherwise, it matters what you drink and how much you drink. Drinking excessively is obviously more likely to cause a hangover than drinking moderately. You get a hangover because the ethanol in the drink causes increased urine production, leading to dehydration. Dehydration leaves behind headaches, dryness in the mouth and fatigue. Alcohol also reacts with the stomach lining, which can lead to nausea. Brandy is considered to be the worst for hangovers. As a result,vitamin B and C are lost so it is ...