The classic Moscow Mule cocktail is super simple to make and it’s a great alcoholic drink to make in larger volumes because it’s mixed with non-alcoholic ginger beer and lime juice. Because it’s so low in alcohol it can be served up in a larger glass but traditionally it’s not served in a glass cup but rather a copper mug.
In short it’s because the mug keeps the drink colder longer without needing as much ice but also because the acidic lime juice tastes a lot more sharp and crisp against the metal cup compared to a traditional pint glass. Glass just doesn’t feel as cold copper and it doesn’t make the lime bite as much either.
Simply put this old-timey cocktail just tastes better (and feels better) when it is served directly out of a copper cup.
Most copper mugs are lined with nickel so the effect is a bit muted but those mugs that aren’t lined (like these) really make the drink pop.
Way back in the 40s when the Moscow Mule was first invented the copper glass was also a marketing gimmick. The original makers of this drink were sales people of both vodka and ginger beer. They decided to use the ginger beer as a mixer with the vodka and serve the drink in a copper mug to generate a bit of buzz.
It worked and as a side benefit the copper cups also helped keep the drink cold and tasting crisp.
As a home bar tender you shouldn’t feel like you have to serve your mules in a copper drinking cup if you don’t have one but if you want the full experience having a small set of copper mugs on hand is a great way to enjoy the beverage the way it was designed.
One complaint from many people who own these types of mugs is that it can be hard to keep them clean. They don’t just go in the dishwasher like everything else. Most solid copper mugs are lined with nickel to make sure they are safe for drinking. This is because copper is a heavy metal which can and will leech into your beverages and can build up into your system in a harmful way.
The nickel lining is a simple and effective way to improve the durability of the copper cup while also protecting you from the unhealthy effects of drinking from copper mugs.
You can read more about why copper mugs are lined with nickel here. This page also goes into more detail on the safety of drinking from copper cups and glasses.