The suction cups are fairly small and in the center, so a drill bit is what is required. You can’t get to the suction cups with a feeler gauge or anything like that.
You will need to drill a small hole near the center, through the area where the suction cups are. One hole for each side. And there may be some hardened metal protecting the suction cups, so drilling the hole may not be that easy.
Plus there’ll be a huge fine for “destruction of government property”. What are you, an anarchist? Parking laws are important and must be respected!