title_body: Can a cup of coffee explode if heated in microwave?
upvoted_answer: As others have stated, superheating can happen in a microwave, especially when using a smooth vessel, e.g. a new, unscratched cup. It is more likely in pure water, but not unheard of from other liquids.
  
  But you need a hack:
  The key to prevent superheating and a subsequent flash of steam when the cup is moved or so is to supply nucleation sites, or, simply put, some rough surfaces or gas bubbles where the water can turn to vapour.
  
  
  Many recommend using a teaspoon in your cup, but at least in some microwave models that can lead to "fireworks" of electric sparks. So questionable at best.
  If you can get your hand at some lab equipment, get one of those glass sticks with a hollow lower end or a little porous ceramic stone. 
  But probably the simplest way is floating a toothpick in the mug.
  Or use an old, scratched mug, provided it is microwave-safe.