It works. Our experiment last night was very interesting and exciting. If one can boil water in a bottle, that means, using the same procedure, a person could cook stew or soup in a plastic container, suspended over the fire.
I was fortunate enough to find a green branch sturdy enough for such an experiment. The Rhododendron hung out over a suitable campfire spot and by keeping it small enough, I could easily keep it fed.
Also exciting is the cordage I used. By cutting 6 Walmart plastic bags into long strips about 5 inches wide each, and then tightly braiding it, I made a plastic cord strong enough to guy tarps and hang water bottles. The heat from the fire didn't burn it either, as I had feared. It actually seemed to solidify it into tougher cordage.
The cowboy coffee this morning was excellent as well. Fill a empty coffee can with water, build the fire around it, still keeping it small and manageable. Place a metal lid on it to keep ashes out. When the water comes to a boil add plenty of ground coffee (not instant) and allow to boil another 5-6 minutes. I used about one tablespoon of coffee per 12 ounces water. Remove from the fire so that the grounds settle out to the bottom. Slowly pour from the can using a pot holder. The ridge in the metal can keeps the grounds from pouring out.
Save this can for the next trip, or recycle and take a clean one.