I took a quick look at the Qwik-Mix link and it looks like you buy it in concentrated form and dilute it with water. That would eliminate a lot of plastic waste so it's inching closer to eco-friendly. I didn't see what potential toxins might be in it, but there was a warning label shown on the image of the bottle so it obviously contains some kind of gick. Not methanol apparently - it must not be freeze-proof as the directions on that Amazon link said to add methanol in cold weather. So we haven't gotten away from methanol yet.
I think it may not be too difficult to use a non-toxic product in warm weather. Probably a vinegar-water or vinegar-soapnut (or castile soap)-water solution like you might use for window washing in the house could do the job. Unless the baked on bugs are resistant to that - I haven't really checked, as to be honest the toxicity of windshield washer was a bit of a blind spot for me and I never questioned it until two days ago when I posted the inquiry that started this thread. Here, the summer wash fluid is some kind of pink gick and the winter is blue. The blue has the methanol. Not sure how else they differ. I think maybe the pink has more soapy stuff for bugs. Still toxic though.
In the big picture perhaps this is not such a huge issue, but in the context of starting to look at one's own lifestyle and try to find ways to transition away from industrial products where possible, pretty much anyone driving a motorized vehicle whether fossil fuel or electric needs to use this stuff. And many of us live in places or have personal circumstances that require use of a vehicle. I assume the relatively low numbers of responses to this thread mean that I am not the only one stumped by the question of what to use instead of the industrial gick (although Dave Burton definitely found some good leads, and thanks for that!). Unless one is distilling alcohol at home, there don't seem to be a lot of home-made options.
I'm thinking the risk of experimentation is kind of high, in winter. The risk of either destroying the fluid delivery system through freezing/expansion, or suddenly driving blind on the highway because unable to clean the windshield is potentially both dangerous and an expensive repair. I'll probably end up continuing to use blue gick this winter. Qick-Mix appears to be out of stock on Amazon, plus considering one then also has to add methanol, the main advantage of that product seems to be reducing plastic waste. Which in itself is good, but not the whole story. Playing around with formulas next summer to start to find a better way to do this during the non-freezing season might be the way to go, and worthwhile even if using a more toxic formula in winter.