The question would be: Which one would be the cause and which one is the effect?

I am diagnosed with ADHD and I consume unhealthy amounts of sugar in form of chocolate, gummy bears and ice cream. I wonder if...

A) all that sugar creates a gut microbiome that facilitate ADHD symptoms or if

B) the general impulsiveness and higher-than-usual glucose demand from the brain create the sugar cravings, or if

C) it's some kind of feedback loop and bad habits get reinforced to the point of addiction

Sugar helps fuel a nervous system that is lacking energy from constant stress and overwhelm.

Chocolate will release serotonin but you need to binge quite a lot of it.