Breweries do water their beer down, literally. American Macro-breweries will brew their standard lagers to higher alcohol contents and then add water to bring the beer down to 5% (or whatever the stated alcohol percentage is for a given product).
Drink plenty of water. Have at least one 16-ounce glass of water with every 12-ounce beer or 4 to 6 ounces of liquor, for example. Water can replenish your fluids and help you stay hydrated.