I'm a little to late to be the first to tell you that these cups are a BAD idea. Plastics are made from a variety of volatile (will evaporate fast when heated) compounds that can end up dissolved in your coffee.

I suggest taking a hot drink cup with you and pouring IMMEDIATELY into a cup that will not contribute to your risk of cancer development.  (I am already to old to end up taking care of whatever children you might leave behind as orphans!)