I find the 8 mg of caffein in an RC cola a pleasant boost. Since I'm now diabetic, I changed to diet RC in 2008 after the bad news. Diet RC was discontinued, the closest substitute now is Pepsi Zero. I'm expecting with trepidation Pepsi's Zero reformulation to add the cocoa that Coke Zero just added. Red label coke Zero made my teeth sticky. Diet Mountain Dew has same amount of caffein, plus some citric acid, no sugar. Over a liter of either drink at one meal feels weird, whereas 2 L non-caffeinated punch doesn't.
As far as the electrolyte, my leg cramps in my sleep in mid-summer if I don't consume some KCl. Gatorade & Powerade took 5/6 of KCl out the product 15 years ago so football players could chug gallons of it along with mounds of sugar. None of those for me. I salt my sandwich , Hormel entre or ravioli with a shake of Morton's lite salt once or twice a week July-September. As a HBP person, I don't need NaCl. Plenty of NaCl in bread, that Hormel dinner, or nearly any other packaged or restaurant food.