I am, to be clear, far from an elite athlete. Nor am I looking at performance *gains*; rather, *avoiding side-effects*. It's not fluid alone because there are many days water is just fine but days it's not (eg, if I'm riding only one hour, I use water; I only use a mix if it's 1.5 or more). ↵
I have NOT performed the experiment with different mixes. I suspect the sodium is a good part of it (because of sweating). So some kind of water+ is what I need; exactly which kind, as careful experiment, maybe a blinded experiment (eg, having my wife prepare different mixes), I have not tried!