Don't know why, of course. Only the numptie(s) who placed the make believe soda cans know.
But perhaps it is a message to the world that every Boeing Airbus product that comes out of that factory can potentially have a bomb implanted in it and thereby ANY Airbus is not safe anywhere.
They've gone to the core where every plane of a certain brand in the eyes of the public could be sabotaged before it even goes into service.
Not that it COULD be, realistically, but the optic of the find in the factory could leave a far-reaching impression that they (perhaps IS) hope could hit air travel in a macro way...?
There also is, of course, the "message" that there might be any number of IS saboteurs who are working for the manufacturer as moles.