I got to thinking about Fiddlehead's recommendation to carry a styrofoam cup for coffee and really couldn't come up with a good reason against it except durability concerns. So.....
Use a 'Go-Paks' snack container and a ten-ounce styrofoam cup.
Pinch the lip of the cup all the way around to make for an easier fit, press it down by hand as far as it will go, turn it upside down on a flat surface and give it a good smack. Voila! Insulated coffee cup.
You can even get fancy with coffee filters or mugmates for 'Cowboy coffee'.
Finished project is .65 ounces/18 grams.