I try my best to avoid insulting people, but the person who filmed this How To video is stupid.
I might be stupid too. I have been operating under the assumption that heating liquids in PET plastic bottles was a proven health hazard. When I took the time to try and confirm my assumption, I was surprised to find out that I couldn’t. PET water bottles are a BIG problem for the environment. Something like 85% of them are tossed into landfills or discarded into our environment after a single use. But PET bottles have not been a big problem for human health. NGOs are even promoting a water disinfection method for rural Africa using PET bottles and solar energy (PDF). Reusing PET bottles repeatedly without proper cleaning and air drying can put you at risk of ingesting dangerous bacteria.
I still contend that it is unwise to throw a plastic bottle of water on an open fire and then drink from it. I managed to find a few quotes from chemists and food scientists saying that they make a personal choice not to consume food or beverages that are contained in plastic. If any of my readers know of any new credible research into potential health risks with reused PET bottles, please let me know.