Build Your Own Thermos Bottle

Here is an article showing how to make your own thermos. Not sure how practical this is for most of you, but this seems a way to make a pretty good one using a standard plastic water bottle and a 2-liter bottle. Epoxy is the insulator.
http://www.ehow.com/how_5007524_make-thermos.html

https://www.freepik.com/free-photo/thermos-fitness-bottles-water-top-view_10828733.htm