Or if your car is parked near someone elses house, maybe they'd be kind enough to let you use a hose there? If they're not on a water metre it's even better. I live in a block of flats and my car is also not parked near my flat (plus I'm on the top floor so it's a right pain to lug water down in buckets and watering cans!) Luckily, a number of my neighbours who live in the houses near where I park my car have offered to let me use their outside hose so that's how I do mine. There are still nice people out there, might be worth asking.