I used an MSR international stove when I was homeless. 1L of some sort of fuel (it takes gasoline, white gas, kerosene, etc) would last me at least a week and

I used an MSR international stove when I was homeless. 1L of some sort of fuel (it takes gasoline, white gas, kerosene, etc) would last me at least a week and at least one form of fuel it accepts can usually be obtained somehow from somewhere. If you can come up with 1 gal gas / person / month it will cook rice or boil some meat easy enough. Of course if there is not even enough gas for 1 ga / person / month I think you are in deeper shit because there's not enough to even transport basic needed supplies and you are probably using mules like in Cuba (in which case, hopefully you can chop down a tree for wood).