Why should you put a bottle in a parked car tyre when travelling alone?

I’ve got no idea. Are we looking at plastic bottles, or glass bottles for defence? If it falls out, it could be considered littering as it rolls across the floor. It seems very strange and I can’t see what this achieves. Are you supposed to hear the bottle if the car approaches you if you’re on foot? Perhaps you’re supposed to leave money in it in the hope that the person who finds it is a shaman and will bless your journey. Or maybe the person who finds it will offer to accompany you on your journey so that you’re not travelling alone any more. It’s a very odd practice. Maybe the interviewer hasn’t thought the question  through properly. Perhaps you’re trying to confuse a thief as he’ll see that someone else is already trying the same scam that he is to lure you out of your car and it’s therefore being watched.