Bizarrely, I had replied to this but it must have been lost in the ether.
Someone spraying your car even by accident is a problem that they have to deal with – the fact that they don’t mind doing it to their own car or their windows is of no interest to you.
It’s hard to ask someone to be a good neighbour when it clearly hasn’t occurred to them that this may be their fault – or that they have to change their behaviour – but that’s what you have to do.
Follow Whale’s advice but if that doesn’t work, start sending them bills for getting your car washed, see if that does the trick. And have a word with your strata manager or EC. There’s almost certainly a by-law being breached here and the neighbour has to take responsibility.