To me that really looks like reactive hypoglycemia, I mean, it doesn't have to drop dangerously low, but just the experience of it soaring and plumeting so much within such a short space of time must produce some really unpleasant feelings. (In my own experience, I feel dreadful at 4.3 mmol/L and pretty great at 6 mmol/L so I really think it could have an effect).

P.S. Maybe you could do the same test on your friend/family member who doesn't suffer from sugar regulation problems, and see how their graph compares. I am planning to do this, and suspect it will be significantly smoother than my own.

P.P.S. The fact that it stabilises in the evenings, could be related to adrenal hormones? I know very little about this, but I have read that hypoglycemia is related to adrenal fatigue, and that people with adrenal fatigue tend to feel better in the evenings (I think because the cortisol output is higher). But google it, I'm not sure.

Every person I have known with Reactive Hypoglycemia (myself included) and every study I have read on the subject confirm that blood sugar stabilize in the evening.

Not only that. Breakfast and morning are the worst moment in which to introduce carbs in the diet, simple carbohydrates consumed in these hours can ruin the whole day. On the other hand it is possible to be far more liberal in the dinner without having symptoms. I have never experienced a sugar crash after 8.00 pm.

Studies confirm that we are insulin resistant in the morning and several readings of mines (among friends too) confirm that blood sugars are not low in the morning. Since blood sugars are not low in the morning, eating at waking time results in probably the worst spike and crash of the day.

So in the evening blood sugars tend to be lower (which is why they tend to be higher, it's a paradox but if they're lower per se they won't spike and crash, the reason they are lower the rest of the day is that they're crashing because they're actually high) and the body is more insulin sensitive, the whole body by cyrcadian rhythms alone is simple less reactive and more in a rested state, whereas in the morning it is less relaxed and more alert.

I have completely removed breakfast from my diet. I wake up with high blood sugar and insulin (because of glycogen release at night) and I let them settle. I'm a bit foggy in the morning but if I wait 60 minutes and drink water it goes away. At lunch I'm reading to eat. My sugar and insulin is more stabilized and I can eat without extreme consequences.

After discovering this (it's a myth that breakfast is the most important meal of the day and that you need to raise your blood sugars when you wake up) if I have breakfast it's very low carb and fat dense.

Bacon and eggs, heavy cream and yogurt, brie and fatty sausages, half-&-half and mascarpone.

I know one thing for sure: these meals can't possible cause an hypoglycemia episode of a sugar crash.

Fat is the only non-insulin macronutrient.
Proteins require almost as much insulin as carbs as need to be kept low in an hypoglycemic diet (not so low to cause a protein deficiency of course)

I don't think that people with hypoglycemia feels better in the evening because cortisol is higher. Anxiety is caused by an excess of cortisol, so if we're experiencing anxiety in the morning, it means out cortisol is too high rather than too low.