How do you eat a thermos flask?

To set about eating a thermos flask you would first need to recognise what the flask is made of. The simplest thermos will have an inside layer of glass, surrounded by air, surrounded by an outside layer of glass, with both these layers covered in Mercury or something similar, and the whole thing covered in plastic or metal.

The first step in eating the flask would be to separate all these layers. Heavy tools will help to smash the glass and mercury and remove them from the tougher outer casing.

Glass can be broken down and eaten pretty easily. Some people have a party trick of eating lightbulbs or wine bottles, and they can do this because it won't actually cut your mouth like you think it would. So long as you chew in a slow, controlled fashion, and use your tongue to adjust any pieces that feel sharp against your mouth, you should be able to eat the glass pretty easily.

The mercury should also be pretty easy, as the layer will be thin and crumple up with little effort. This layer is also probably poisonous, so it is recommended you leave eating the mercury til last.

The outer casing will provide the biggest problem, as it will be made of a robust material that cannot be easily chewed or digested. If it is plastic, then a particularly strong grater will be able to prepare it for eating as a condiment on your usual meals. If it is metal, then you will need to ask a local blacksmith or anyone who works with hard machinery to reduce the metal into filings which can be used in much the same way.