The chocolate and cakes also have a high fat content (generally). Fat slows gastric emptying, so, while you were taking on carbohydrates, they were less available for your body to use.
You only need carbs during exercise. Reduce your fat and protein intake.
rode 220k yesterday. ate every hour, alternating sugar (choc/crap cakes) and carbs (soreen/clif).
energy levels still madly fluctuating. I think I need more sugar. or more carbs. which? who knows