(It's probably just regular glass cleaner in a fancy bottle, but again, not expensive so its not a bad idea to try that if you do decide to use a cleaning product). it's designed to not harm lenses coated with anti-scratch, anti-glare, tinting, etc, etc so it's likely good for something like this. CleanMyMac X packs 30+ tools to help you solve the most common Mac issues. Clear your Mac with Mac cleaners automatically (Free and paid) 1. Oh, another option would be cleaner used for eye glasses. Delete megatons of junk, malware, and make your Mac faster & more organized. I'm not sure what, if anything, the iMac glass is coated with so I can't say that using glass cleaner is good or not, but just for the record, my CRT HDTV says not to use glass cleaner on it either, but I do and I've not noticed any ill effects on the coating. It's cheap, like 50 cents t $1 a gallon at most grocery stores, so worth a try anyways.

A lot of the streaks and spots on glass after cleaning are residue from particulates in water so you can eliminate that by using distilled.

Try distilled water on the cloth (just good and moist, not sopping wet - you don't want to leave behind any drips as you wipe it) and see how that goes.

Imac cleaner