Commercial glass and window cleaners seem inordinately expensive for what they are, which is mostly water! I’ve been using this formula for several years, inside and out, and my windows and mirrors come out squeaky clean. We are on a well and our water is hard. If wind causes water spray from a sprinkler to spatter the windows this will remove watermarks as long as I clean it within a day or two. Adding the blue coloring does not make the product any more effective, but its color makes it easily recognizable as glass cleaner. (And, I think, more fun to use!)
2 cups water
1/2 cup distilled white vinegar
2 drops dishwashing liquid (without moisturizer)
2 drops blue food coloring, optional
24 oz. spray bottle
Add ingredients to spray bottle in order. Close the top and shake well. Label with name of product.
Additionally, I write the formula (recipe) right on the bottle – or on a wide piece of masking tape affixed to the bottle. This makes it simple to mix up a fresh batch as needed without having to hunt for the recipe.