Nope. Never heard of anything exactly like that. Most folks find that riding immediately after a large breakfast is a bummer, though a small breakfast is fine and immediately is key. But you feel good at the start and during, right? Usually 1.5-2 hours is the minimum wait after a large breakfast, 2.5-3 is better for one's blood sugar to settle down. It peaks after breakfast then drops, right? So if you start when it's peaking, you're fine, but if you start in that low BS valley, not so fine. In any case, doesn't really sound like that's the problem. My guess is that you aren't drinking enough on that climb and your stomach osmolality is too high. You don't say what your drink mix is, how strong it is, and if it contains electrolytes. Are those Medjool dates? If so, they're 18g of carbs each, or 144g or 576 calories per hour. If that's the case, there's the problem. To start with, it's hard to digest on a climb. 60g of carbs/hour is a pretty normal average, but most folks probably can't manage that on a climb. And only fructose isn't a good way to go. I think optimum is about 2 sucrose/1 fructose. They digest on different pathways.
My advice is to cut way back on the dates, add a sucrose source. Figure how many calories per hour you're going to ingest and stick with that program, weighing your food if necessary. I do. Take extra of course. Drink plenty of plain water, and either take electrolytes or put them in a water bottle. I use Hammer Endurolytes, probably not easy to get in Switzerland. I'm a profuse sweater, though my sweat isn't salty as I use a relatively low-salt diet. I take 2 of these capsules/hour on hot rides:
Endurolytes Capsules
Supplement Facts Serving Size 2 capsules
Amount Per Serving
Sodium (as Sodium Chloride) 80mg
120mg Calcium
100mg Magnesium
50mg Potassium
50mg 1Manganese
So something like that. Electrolytes help the stomach empty by making its contents close to isotonic.
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