I use Dawn Platinum and I put 2 Tablespoons in a 5 gallon bucket or a quick line across both sides of my mop before getting started. Don’t need more than that. This is what I tell any client that asks what I use.
Dawn has been used for decades to remove crude oil from animals during marine accidents/spills. It is the ultimate degreaser that does not leave a residue or harm the surface or animals. What is the most common marking on a piece of glass that needs to clean off? Hand prints. Which is nothing more than our body oil smeared on the glass. So if it is strong enough to remove crude oil without causing damage, then it should be more than enough to remove body oils from glass.
Test this out next time, touch a piece of glass in front of a client and leave a hand print, wash your hands with dawn and dry them off with a clean towel. Put your hand on the glass again. No hand print.
Also, the makers taut it to leave a streak free shine on dishes and glasses, same holds true for window glass. It also rinses away without leaving a residue. I have found that some of these window cleaning chemicals that are marketed to consumers have an evaporative component like alcohol or ammonia, and a second component that leaves a film on the glass even after being wiped. I believe this is supposed to be a lubricant for use with paper towels. The problem is, this film is left behind on the glass and it attracts dust and dirt, allowing those particles to adhere to the surface more quickly and therefore the window is actually dirtier, faster. So then you need to use more of their chemical to clean the glass sooner, and it is a perpetual cycle for the consumer to use and buy more of their product.