1) Food
purchased solely to be used in a protest. One is 'crowned' with the (usually rotten) food. Hence the word coronation. Out of date quiche is readily
available and can be thrown in an aero-dynamic way.
2) To spend
other people's money on something that you want and they don't. In this case it's not the food that's rotten, but the source.
3) Rotten food.