How to Warm Up Cold Coffee?

Problem: Cold Coffee

Today, I made a great cup of coffee as usual.  I used my coffee grinder to make fresh coffee grounds from whole bean coffee.  I used filtered water, and brewed my coffee in a coffee maker with a cone filter for maximum flavor extraction.  Here are details on how to make a great cup of coffee.

I got distracted in my workshop, and found that I had about 1/4 cup of cold coffee.  I like my coffee hot.  I have tried heating up cold coffee in the microwave, but it tastes terrible.  What can I do to warm up cold coffee without making it taste bad?

My coffee got cold- how can I warm it up?