A soda can with 50 ml of water is held over a burning potato chip of known mass. A thermocouple reads the temperature of the water, and its change, to estimate the energy content of the chip.
Other burnable foods include nuts, e.g. brazil nut, and other kinds of fried snack chips.
The heat transfer from burning chip to soda can bottom is only so good, and the temperature rise does not match that expected in the ideal case.