A thermos is about the only option for hot stuff. However, I brew my own using the GI-issue canteen cup and cooker with a trioxane bar. To protect the wood of the stand, I use the top off a can of sardines (another staple of tree-stand eats!) under the trioxane bar. For coffee I use those coffee bags, similar to tea bags, from Folgers. I swipe powdered creamer from the snack bar here at work.
The other thing to consider about coffee is what happens later. If you don't want to whizz off the stand and leave a stink for the deer to find and avoid (not to mention the effect if the wind is in the wrong direction), I make "piddle packs" similar to the ones military pilots use by putting a cheap, disposable sponge in a Zip-Loc baggie. I toss it in a dumpster after use.