Beer mug represents casual drinking, bar culture, and 'cheers' sentiment on its own (without a second mug for clinking); part of the original 2010 Unicode set, it's often used instead of the clinking-mugs version simply because it's shorter to type or search for on some keyboards.
Keywords: alcohol, ale, bar, beer, booze, drink, drinking, drinks, mug, octoberfest, oktoberfest, pint, stein, summer