why do you use copper mugs for mules
Moscow mule The Moscow mule is almost always served in a copper mug. The popularity of this drinking vessel is attributable to Martin, who went around the country to sell Smirnoff vodka and popularize the Moscow mule. Martin asked bartenders to pose with a specialty copper mug and a bottle of Smirnoff vodka, and photographed a Polaroid picture of them. He took two photos, leaving one with the bartender for display. The other photo would be put into a collection and used as proof to the next bar Martin visited of the popularity of the Moscow mule.[3] The copper mug remains, to this day, a popular serving vessel for the Moscow mule.