I have certain foods that seems to dramatically change the way stimulants like caffeine affect me. For whatever reason if I eat bananas and nut butter (maybe I have an allergy or food intolerance?) I find that caffeine makes me feel like I crash. When taken on an empty stomach I can get very "wired" but it also depends heavily on my sleep schedule and the time of day I take it.
I've noticed I can get an incredibly productive boost from caffeine when I take it at a time that disrupts my current circadian rhythm. I (used to) usually drink coffee in the morning and it rarely felt like it helped at all. I knew if I was desperate I could drink it around noon and see a big boost but then I wouldn't be able to go sleep on time and would pay for it the next day
Genetics, diet, microbiome, epigenetics, sleep habits, study habits, social health, seasonality, etc all likely play some role in the way people metabolize caffeine.
There is no published evidence that stimulants universally make people ADHD more tired or calm.
And personally I believe given the right conditions anyone might get to experience the effect of caffeine actually making them sleepy.