What is the ruling of the Sharia on car park attendants who work randomly in public streets and force people to pay?

If people perform work for you without a prior request or agreement on a wage, you are not obligated to pay them, and whatever you give them is considered a donation from you. For whoever works for another with their permission without an agreement on a wage, they are entitled to a customary wage. As for whoever works without permission, they are not entitled to anything because they are considered a volunteer.