As you've probably noticed, I like pocket kits. And I was disappointed with the aluminum foil performance too. So far I've found 3 reliable solutions for a boiling pot improvisation from a flat pocketable stuff.

1. You can boil water using burning hot rocks placed in almost any container filled with water (e.g. carved piece of wood, waterproof hat, just a depression an a rock...). Even a plastic bag could work if you place the rock into an isolating screen (made from branches for example), so the rock can not touch the plastic.
2. Replace the cheap aluminum foil with a thin sheets of aluminum, which is easy to procure from large beer cans (I like Asahi cans for some reason smile they have a very thin and lightweight sidewalls). You can rig a very sturdy pots with these sheets.
3. Cut open a stainless steel hip flask (plan to try that with my 8 oz one, which fits most of my pockets very comfortably). And make a lid, folding handles, and a hanging wire for it.