On my thermos, there is no need to remove the stopper. It has a very small popup spout (much like some water bottles) that you can pour the liquid out of.

I usually get a good fill of coffee in the am before I start our hike. Bringing the thermos of coffee is for days where we do not stop for a hot lunch or dinner and it is nice to be savor a cup of coffee at anytime without the hassles of carrying a stove or making a fire