Rumour has it, that the plastic nozzle of a can of expanding foam, it flattened slightly to fit a coin slot, is more than capable of pumping a parking meter full of foam in no time flat.
I used to live in a suburb where the local council thought parking meters would be a great revenue stream, they even borrowed several hundred thousand dollars to install them.
The cost of maintenance, accounting and enforcement ended up being higher than revenue, and that council went bankrupt yet again.