The Glycemic Index is measured in rest and consumed pure.
This being said, the insulin response to carbohydrate intake during
exercise is a lot complexer.
It's not only digestibility and rate of digestion and uptake but also
the rate of stomach clearance. Sure enough if you eat some glucose and
your blood sugar will rise sharp but add some fat to that and it won't
rise as fast simply because fat makes stomach clearance slow down. (by
inducing a higher tonus in the pyloric sphincter if you must know)
An added problem would be that your digestive system doesn't respond
anything like it during exercise then when at rest, mainly because of
reduced bloodflow in the entire gastrointestinal system.
In short, modest glucose intake during exercise doesn't cause a high
insulin peak and blood sugar drop as a result. There's no reason not
to use glucose as an energy source.
Whether the slow digestable carbohydrates offer an advantage in
performance or not is heavily debated. In all likelihood it will
provide you with the exact same energy and results. It is however very
much recommended to keep your simple carb intake prior to a race or
training as low as possible. Prior means at rest and that WILL yield
an insuline peak and blood sugar rebound drop.
Honey is a great low GI product and mixes rather well with things like
a twist of lemon juice. Try and see if you can hold it down on the
road, there's no rule of what can an cannot be tolerated, it basically
depends on your own body. The rule of thumb about the 7% solution is
somewhat arbitrary, I once read an article about how that exact number
came into play.
More information about sugars and exercise here :
http://www.runnersweb.com/running/news/rw_news_20060620_ERB_Carbohydrates.html