Have been parked where a sprinkler has been hitting the side of our rig and the spots have built up. I have tried the vinegar trick but to no avail, so I hope some one has had success with a easy to apply product.
If this isn't the right forum I would appreciate it being moved.
When I put some redmax pro on the cap of my 5er, had some tough water spots on some windows. I found the white 3m scrub pad and barkeepers friend did the best job at removing them.
General hard water spots I like the Meguiars cleaner wax. If the spots are hard water iron deposits I find mixing 1/3 cup of Iron Out to a 10 quart pail of warm water works well.
I'd recommend Meguiars products. They sell a water spot remover. I haven't used that particular product, but I've used other products from them and been satisfied. Auto supply stores generally carry Meguiars, as well as Amazon.
Retired and visiting as much of this beautiful country as I can.