On the bike I do one bottle Nuun, one bottle water. Nuun on the down tube, be so I know which is which.
Off/after the bike, I use a few vacuum insulated water bottles. I put ice and Nuun in, add cold water. Don't keep them in the fridge and the insulation works too well for that, so I have a pitcher of cold water in the fridge to make Brawndo with.
It seems like after 10 or 20 minutes, the fizz is gone. I've come to like some of the flavors. I got some cheap electrolyte powder that was on sale at the grocery store, it was awful.