(This is mostly notes for my own use, although someone else with similar problems with sugar might find them useful).
Most/all running foods suggested are sweet, or at least carb rich. I have a bit of a problem with carbs. It's most noticeable with sugars (esp glucose) but happens with starch too. About half an hour after ingesting a lot of carbohydrate I get cold sweats, shakes & disorientation. It sounds a lot like diabetes but isn't (I've been tested over and over, and I've had this since childhood. A doctor friend suggested it might be dumping syndrome).
Mostly I just don't bother eating when running, and that's fine up to marathon distance. In fact I'm doing much better at longer distances since stopping trying to eat. Now that I'm looking to do short ultras I need to find things I can eat. Lately I've been shifting my diet to be more protein rich (whilst still avoiding saturated fat, and in any case I'm a vegetarian), so on yesterdays 50km run I tried out the following:
* Hard boiled eggs (gave me a little acid, needed washing down with water, but no ill effects)
* Chia seeds (nice to chew on, tasted pretty good, extremely portable, no ill effects at all)
* Walnuts (the body went NOM, they felt like just what was needed. No ill effects)
I was pretty wiped out at the end of the run, 50km is a lot for me at my current fitness level, but I didn't have any blood sugar wipeouts, and wasn't madly hungry at the end. This looks like a promising line of experiment.
Edit: Much later (Aug 2019). Peanut butter, in refillable baby food pouches. Worked a treat on the Brecon 50.
