I do not mean to invalidate your experience, but generally speaking it seems like both no and yes to sugar rush/sugar crash.

"Double-blind trials have shown no difference in behavior between children given sugar-full or sugar-free diets, even in studies specifically looking at children with attention deficit hyperactivity disorder or those considered sensitive to sugar. A 2019 meta-analysis found no positive effect of sugar consumption on mood but did find an association with lower alertness and increased fatigue within an hour of consumption, known as a sugar crash." [0] [1] (emphasis mine)

[0] https://en.wikipedia.org/wiki/List_of_common_misconceptions#... (yes, I know.) [1] http://wrap.warwick.ac.uk/115618/1/WRAP-Sugar-rush-crash-met...

Sounds like typical spike-and-crash style diabetic response to me.

Yes, I am diabetic.

That was my thought exactly though with younger kids this can be less simple due to size and response times of different parts of the digestive system. Though raising the blood sugar levels of non diabetic even by a few mmol/l can have significant effect where diabetics can have far larger swings an notice it less.

TBH, I don’t notice when my blood sugar is high. I only notice it when I crash. That’s why I’m trying to get better about using a CGM to keep a closer eye on my blood sugar, even though I’m not on insulin. My hope is that the CGM can help me notice patterns in my diet that I can then change, so that hopefully I never end up needing insulin. But this is a work in progress.

You gave a 4 month old sugary fruits? I thought you have to wait for 6mo for dietary diversification.

You wait as long as seems reasonable for you. It's your child after all, they're all different.