[Jake6655]

If you can get rid of the residue left by commercial window cleaning products, simple Soda Water is a fantastically effective and cheap alternative.

To get rid of the commercial cleaner residue, wash windows with hot water with a little washing up liquid in then rinse with a capful of distilled white vinegar in warm water. Dry with scrunched up newspaper.

Once that's been removed, you can use just the soda water in a plant misting spray. Spray on, wipe with a cloth and dry with newspaper.