When you return to your car, that has been parked under a shade tree all day, you find your windshield covered with bird droppings! Ugh! After you remove most of this with your wipers, pour club soda into a spray bottle (keep this in your car if this is where you regularly park) and spray the soiled area. Let it sit for a minute or two  then wipe off with paper towels. The carbonation in the soda will dissolve the mess easily.