During the CSOB Bratislava Marathon I tested a new brand of energy gels, the very same that were used by Polish National Winter K2 expedition, Spring Energy. One of the ultrarunners, whom I follow, Sage Canada, is an ambassador of this brand.
These are made from natural ingredients and have a taste of fruit mash. Because of that the expiry dates are only a few months. Packages are of a medium size 35-45g and 90-110 kcal. Placing it in the mid-range of available products. These are not as sweet in taste as some other gels and better tolerated by the body under stress. According to the manufacturer it prevents insulin spikes giving more balanced source of energy over time.
I can attest I had no problem eating and digesting these during the race. These do not require as much water to drink with as some of the other gels I have tried before.
I am sure to take a few for my mountain trips in the future. Available at http://myspringenergy.eu/