They make small butane torches made for soldering. Pocket size but you have to be careful with them. Don't put anything painted or plastic in the direct flame. You can put steel into the flame for faster heating. I would not use coffee to thaw stuff. It will only gum things up worse in the future. Carry a thermos of hot water with you if you only have to go a short distance. The torch works better because it will dry things out. Brake cables shouldn't freeze unless they are full of dirt and water. If you clean your bike off and knock the water off every day and let it dry inside you will rarely have the freezing problems.
Also, if you only ride a short distance on the flat and weight is not an issue a propane torch is the bomb for heating things. Probably weights about 3 pounds though. But makes bigger flame and the larger tank will last a lot longer. But you do need to keep sensitive things far enough away from the flame to not melt or burn them.
http://www.westmarine.com/webapp/wcs...&ci_sku=297044
These small bottles are used for back packing stoves only weigh 1 pound. Then you just have to get a tip:
http://www.google.com/products/catal...d=0CE4Q8wIwAQ#