If I am thinking right you are talking about the empty Mylar bags that the coffee circles come in?
I know of people who reuse Mylar potato chip bags to do meals in....you can even seal the bags with a household iron.
You can as well buy Mylar food bags online rated for food use.
Anyhow, the ones that use the bags do wash them first to remove scents/flavors. Handwashing.
To the comment on boiling water...you don't need boiling water to do instant meals. 180* works just fine if you let it sit for 15 minutes cozied and that is 32* below boiling! The food will still be about 150* when done which is plenty hot.