As a rule of thumb, coffee will ALWAYS taste better when freshly brewed. It is well known that stale coffee should be thrown away and a new cup made, simply because the taste changes after a couple of hours. However, I know there might be desperate situations you have to heat up that stale/cold cup of java.
So for those of you who are need that java fix and are in a precarious position, I present the how to go about Reheating Coffee (cue epic music)!
In the Microwave
Place the cup of stale beverage in the microwave and nuke it for about 30 seconds. You are going to end up with a nice steaming cup; however I can guarantee that will not taste great, possibly ok, or so-so or possibly it will taste bitter or like toxic waste. L
On the Stovetop
Get a pot and pour the stale coffee in there. Turn on the stovetop and heat up the coffee in the pot. Once you feel it is heated enough, pour back into your cup and enjoy!
Once again, If you really enjoy a nice cup of joe, then the best option is really just making a fresh batch. Reheating will really do no justice and if you take this piece of advice for me, then your taste buds will thank you tremendously for it.