We used to make these all the time when riding motorcycles all around the country.
Super simple, Super easy to make, and VERY DANGEROUS if you are an idiot with flammable liquids!
I've used them 100's of times with no problems, but if you are a klutz or have problems with dangerous things, DO TRY THIS ONE!
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Start out with beverage can...
I prefer 'Tall Boys', they actually work better than the 'Standard' size cans...
If you want to cook for more than about 20 minutes, you might want to make more than one and have the next one waiting since it's VERY dangerous to try and refill a hot can!

Cut the top out, and punch some holes in it like this.
Top holes are the 'Burner' holes, bottom holes are the air vents.

Add about 2 Oz. to 2.5 Oz. of fuel, in this case GASOLINE to the bottom of the can...
Most of the time I fill them up to the vent holes, but if you do, be careful when you light it!

Set your food warming/cooking tray on top once lit and cook away.
I suggest you use a covered cooking platform otherwise you will get a gasoline taste in the food.
2 to 2.5 ounces of gasoline will give you 20 to 30 minutes of good hot burn time.
Be SURE to put this thing on something that won't burn!