Enough fuel but stomach empty?
So I noticed that when I don't start riding shortly after my breakfast at home, but instead eat and then drive to a mountain pass, I invariably have an upset stomach upon reaching the top. Fuel is good, I don't feel bad, don't lose power beyond maybe a few watts (but well at that intensity and altitude for longer passes it isn't the sugar intake causing that) and yet when I get to the top I noticed my tummy is upset. Feels like burping helps, which is a sign of air, i.e. empty, I believe. I take my energy from drink mix and dates (and yes, I stuff a 200g, which is 132g of sugar, bag into my pocket and eat a couple every 15 minutes) so carb content is high enough, but obviously there isn't a lot of volume in the tummy. Dates when chewed properly are nothing, the liquid is liquid, that's it. When I cycle from home relatively shortly after breakfast, even riding two hours and then doing a 1 hour climb, I do not get an upset stomach.
Is this a thing? I mean it is just 1.5-2 hours that pass in the car, not using much energy there, so it must also be a filling issue, can't be that in that time all the breakfast energy is used up. I am already thinking taking breakfast with me and just eating a normal amount right in the morning. But also, maybe looking for other options to take with me during the ride, stuff a crustless sandwich (I love bread) into my back pocket or something. Can this be a thing? Anyone ever came across it?