A retort bag would be better. They are foil/plastic melded together. They will take the heat of boiling hot water without losing their structural integrity (melt). MRE pouches are retort, as are the freeze dried bags that actually direct you to add hot water to the bag with the food in it to re-hydrate.

Unfortunately retort bags are not easy to come by.
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The ultimate result of shielding men from the effects of folly is to fill the world with fools.
-- Herbert Spencer, English Philosopher (1820-1903)