In the winter I usually keep several small bottles of water (individual ?16 oz?) and I can use a small Esbit stove & canteen cup setup with Triox tabs, or my favorite is an old swiss mil surplus camping stove setup. Just keep that thing with my backpack wherever I go...
The swiss stove works with denatured alcohol, or for a 'mulitpurpose' fuel, you can just keep a small bottle of everclear in there!
Disinfects wounds, cooks food/MRE's, boils water, melts ice, and a small bit mixed in some water with a lemonade/citrus/gatorade packet helps with a little bit of 'trail aches' after you've been walking through the woods all day long and your ankles/feet/back are feeling their age.
Weighs a bit more than many ultra-lightweight camping stove setups, but I like the efficiency of fuel use, and versatility.