Howdy Lipbiter
Well, you can be sure that sardines will never be in my daypack
As you can see from the replies, everyone has found what works for them to supply calories, water, and electrolytes. I recommend trying several different sports drinks (Perry makes his own), bars and gels. There's also no substitute for the enjoyment of "real food."
When I hike Skyline or a long day hike like Whitney, I carry Gatorade Endurance (higher sodium content than regular Gatorade) in my CamelBak. I take in about 1 gel per hour -- alternating between caffeine free and caffeinated. I really like the PowerBar double latte gels which provide 50 mg caffeine and Gu vanilla gels. I usually stick with gels and Gatorade while climbing.
I also carry baked Nacho Dorritos and a turkey and swiss sandwich on Wheatberry bread. These are my treats for the summit. In the winter, I'll carry hot chocolate in a pint thermos.
Red Bull only has about 80 mg of caffeine per can. I don't use it because I don't like the taste. Many other so-called "energy drinks" such as Monster and RedLine have much more caffeine -- 200 mg per serving. Often a serving is only half the bottle. I don't recommend them because they often contain many unproven ingredients (see Cynthia's post about picking up trash).
1% fat chocolate milk is an excellent recovery drink -- it supplies both carbohydrate to restore muscle glycogen and protein to aid muscle repair. Also tastes good and is cheaper than many "recovery" products like Endurox R4.
As my hiking friends can attest, beer is my favorite drink at the tram after Skyline

One fellow I introduced to Skyline calls it the "hike to beer heaven." I think I recall Walt saying that hikes in Scottland always finished up at a bar...
Miles of smiles,
Ellen