The simple answer is YES, you can microwave your leftover cup of morning joe - but don't expect it to taste as good as when you first brewed it.
While some people don't even like coffee, those who were born with or acquired the taste will be quick to say that microwaving coffee compromises the complex flavor profile of this bean-derived beverage.
The coffee microwaving debacle gets thrown into double jeopardy if it's a dairy-based coffee you want to reheat, such as a latte or mocha.
Heating at too high a setting or for too long will lead to scorched milk - not pleasant to drink.
Of course, the important thing is that microwaving your cup of mud alone is in no way dangerous to your health or safety.
The worst that will happen is you'll probably get a bitter aftertaste even from the choicest blend of beans.
Caution: Contents Hot!
It's crucial never to microwave any plastics or other harmful material that can melt. Microwaving plastics, such as the lids and straws from your favorite coffee shop, will lead to them partially melting and leaching into your drink.
Consuming plastics is known to increase cancer risk, which shouldn't be part of anyone's coffee-drinking experience.
Metal is another no-no for microwaving, as some have learned the hard way by making sparks fly.
You can usually find out if a cup is microwave-friendly by checking the bottom, which is most easily done before filling it up with old coffee.
So How Long?
This depends on a few factors relating to the microwave, the cup, and the coffee itself.
As for the coffee, it obviously matters how much joe you're microwaving at a time and its temperature.
Microwave power and the thickness and material of the cup are also variables in play.
As a general rule, 45 seconds is a good starting point when trying to put new life into your stone-cold coffee; if that doesn't do the trick, you can put it back in for 30 seconds at a time until your brew is in the perfect Goldilocks zone of hot beverages.
This is generally a better idea than smashing the minute-plus button a few times, walking away, and forgetting about it. Your coffee's flavor profile will be even further compromised if you have a burnt tongue.
Reheating that coffee for a quick breakfast in the morning? Did you know you can also quickly microwave bacon and scrambled eggs (or hard boiled eggs if you prefer) for a tasty addition to your coffee.
But one warning - nursing moms should not warm breastmilk in the microwave.
Sources
https://www.thedailymeal.com/drink/best-way-reheat-coffee
https://dialupthecoffee.com/can-you-reheat-coffee-in-a-microwave
https://spoonuniversity.com/how-to/reheat-coffee-in-the-microwave-how-to
