We're going to try this one, suggested by Sue:

Try this instead of Sterno.

Oh, this is so embarrassing! I thought I knew all the homemade stoves, and I found a new one!

I don't know how I missed it. And it's so simple... it makes a soda can stove look like brain surgery. One version is even at Zen Stoves, but this one has a handy screen that keeps the contents from spilling.

Grab the rectangular Altoids tin you aren't using for your EDC anymore.

Get some perlite (expanded white volcanic stone -- from garden centers) and a piece of aluminum window screening (not vinyl).

Set the open Altoids tin upside down on the screen as a template and mark around the edge with a marker. Cut it out, and trim the corners a bit. Form another piece of the aluminum screening into a temporary cone sieve and put a handful of perlite in it, shake a bit and discard all the perlite that falls through the holes (it's too small). Put the larger stuff into the bottom of the tin. Repeat if you need to, to fill the tin. Lay your cut screening over the perlite and tuck the edges under the rolled rim of the tin.

Add denatured alcohol to the perlite and light it.

BE AWARE that burning alcohol is practically impossible to see in daylight. Let it burn out and cool completely before you close the lid. Wave your hand over it to make sure the flame is out.

Be sure to set the stove on something that is heatproof, and you'll need something fireproof to raise your food/drink container above the flame, like some regular bricks or a circle of hardware cloth. And you'll need a windscreen if you're using it outdoors.

You can use any alcohol, but as HikinJim says in his stove blog, if you use Kleen-Strip® Green™ Denatured Alcohol, it will burn hotter than things like Sterno, rubbing alcohol and Heet, so you can actually boil water. Alcohol also produces less carbon monoxide, so it's safer to use indoors (still, use some common sense).

The Kleen-Strip website and MSDS