I have a car bin that hangs from the gear stick. It is great for all the tissues, food wrappers, car parking tickets, baby wipes etc. I got it on Amazon and it helps enormously. so the car might not always be clean and crumb and toy free, but at least it doesn't have rubbish mixed in amongst everything else.
I clean the car and fill it with petrol every friday without fail. I don't have 3 kids and a dog, but if I did I would probably have it hoovered every Friday too. It's a FlyLady thingy, I do the same with my handbag. Been doing it for years now, helps me clear my head.