The friendship fallout they keep having
ADHD child behaviour
What to do right now
Another friendship has broken. They are hurt and they may not understand why. Do not try to fix it tonight. Sit with them. Let them talk if they want to. Do not say 'you will make other friends' because that dismisses this loss. Say 'that sounds really painful.' Tomorrow, if they are open to it, gently explore what happened. Not to assign blame. To help them see the pattern so they can do it differently next time.
What your brain just did
Your body
Your nervous system is activated. Cortisol and adrenaline are influencing how you think and react right now. This is physiology, not a character flaw.
Your brain
The ADHD prefrontal cortex provides less reliable braking between feeling and action. The gap between trigger and response is neurologically shorter than in a neurotypical brain.
What this did
What happened makes sense when you understand how your brain is wired. The reaction isn't the problem to solve. The conditions that led to it are.
What your child is experiencing
Their body
They are hurt and confused. The friendship felt real and now it is gone. They may not understand what they did that caused the break.
Their brain
ADHD social processing is slower than neurotypical. They miss the cue that says stop talking, the signal that says this joke went too far, the moment when the other child needed space. The social operating system runs on different timing. They are not bad at being a friend. They are running social software on slower hardware.
What they need
Help them see the pattern without blaming them. One good friendship matters more than popularity. Social skills coaching, if accessible, builds the specific skills that ADHD impairs. And regular validation from you that they are worth knowing.