Fill you old spray bottle and wash your windows inside and out all year long.
A bottle of windshield washer from Walmart or a bulk store is far cheaper than the gas station, about 2 dollars for a jug, which is cheaper than the small bottle of Windex and it can be used year round and since you know it is for your windshield you are guaranteed a streak free shine every time!
Another trick to saving money is to always use a rag instead of paper towel for your basic cleaning. My rags include dishtowels, washcloths, and old t-shirts. When done, rinse thoroughly and place your rags in their own bin or pail beside or on top of the washer. When it is full wash your load of rags using my laundry detergent recipe.