Tums.. that is pretty brilliant. I bet they even have a travel pack I could put in my saddle bag just in case I start to feel cramps coming on.
I just checked my kitchen and it's between Emergen-C and Gatorade. I prefer Emergen-C, it has 30 mg less sodium but 8x more potassium. I did drink one 20 ounce bottle of Emergen-C but that was early in the ride. Also I think I may have accidentally taken a diuretic that I thought was just a vitamin (but was instead some ****ty "energy vitamin" that had weight loss enhancers.. ie.. make you piss constantly) so I pissed about 5 times on the trip. Ridiculous.
I guess I just answered my own question. More Emergen-C. I usually refill with hose water from a church on my ride, I will bring two extra packets to mix in for the return trip.