Disclaimer: of course, everything is a spectrum. To ADHD-people, caffeine has varying effects. Some get tired from it, others it affects less or not at all.
Caffeine used to make me sleepy. I'd often have a cup straight before bed. As I get older it doesn't have such a noticable effect on my but even black sugarless coffee really makes low blood sugar issues worse. If I drink it first thing in the morning and eat anything sugarry I'll crash 20 minutes later.