I take an old pair of hose (womens), buy some loose tobacco, cut the hose to about 1 foot, 30cm long making sure there are no holes in the toe or elsewhere, put a 1/4 cup or so of tobacco into the sock, tie a knot so the tobacco stays put. Then open the bonnet of the car, find the windshield wiper water tank, drop the end of the sock into the solution or plain water, make sure the upper end of the sock is securely fastened to something outside the tank so you won't loose the bag you created and you'll be amazed at how clean the windscreen will be next time you use the wipers after squirting the windshield as usual. An alternative would be to boil the sock in water like tea, but don't drink it! after 10 minutes of boiling, let it cool, squeeze the bag so all the "tobacco tea" goes into the pot. When cooled, pour it into your windscreen water tank. As you wash your windscreen with the wipers going the squirted liquid will clean the glass and make rain water sheet off rather than leave droplets. You can actually drive the car safely because you can see as if no rain was falling. If your wipers stop working all together and you can't see to drive, take a sock, as the one I described above, get it wet and wipe the windscreen with it. The rain will then sheet off the glass as if there was no rain at all. no drops can form. The tobacco breaks the surface tension. Want proof? Take a glass of water, fill it to the top just short of spilling over. You'll notice the water actually rises above the edge drop one grain of tobacco or black pepper and the glass will immediately spill the water out of the top of the glass. I keep such a bag in a plastic bag under my seat. You never know when you might need it. You can use it many times before needing change the tobacco. If you just want some cheap glass cleaner, mix a 50% solution of white vinegar and pour it in your window wiper water tank. It will keep your windscreen nice and clean; also streak free.