A little bit of water, bucket, soap/vinegar, washing cloth and a drying cloth are all you need. I caution you though, do not think of this as a great way to get your children to clean your house. I assure you it makes more work for you. (remember either clean up any "messes" with them or clean up when they don't see you do it) The desire is for the child to feel successful when they complete the activity and feel proud they did something useful.
Here is a picture of the window washing I have prepared on a shelf for them.