I don't have any great solutions, but wouldn't attempt anything longer than a half marathon without carrying supplemental fuel. Sports drinks have plenty of sugar, but there's only so much liquid you can keep down.

Clif Bars are energy dense, and the varieties are not equally nasty. White Chocolate Macadamia Nut is the one I find most tolerable, but I carried two of them for 30 miles and never ate them at the 2014 50M.

Gels are about as good as it gets. I recommend trying a few flavors and only carrying something you know you don't hate on a run you care about. I have to plan a schedule and keep an eye on the clock or I will postpone them. If there are no aid stations, I would aim for a gel every half hour or so, followed by fluid. The Clif Shot package has a strip to keep the tear-off tab connected to the packet, which makes them a little less annoying.

I keep some gels spiked with caffeine in reserve for late in the run. Like with Advil, I never feel sure that the drug makes much difference, but sometimes it really seems to help and that is good enough. If it's a warm day or a very long run, electrolyte capsules are also essential. Succeed S!Caps are popular and have worked well for me.