So I was this person, and I didn’t figure it out until later in life.
The trick is, with ADHD, caffeine will slow down your brain but it still speeds up your body (still a stimulant). So too much, and you will be tired and jittery.
That’s why I use nootropics instead of caffeine. Specifically this stuff. (Ingredients)
No jitters, just dopamine. Slows my brain down, takes away the depression, and allows me to actually get shit done instead of sitting in front of the computer all day. A full capsule is too much, but they’re easy to open and extract the powder. I get 2-3 doses from a single pill.
The effects of this particular blend I take are extremely similar to Adderall. It feels like it literally turns off my ADHD for a few hours. Unfortunately, it’s so similar to Adderall that it also has a similar comedown. But for a brief moment, it allows me to be a functional adult, and for that reason alone it’s worth it.
FYI that product is not regulated in any way and is not required to contain the ingredients it claims to have. In addition, it’s a huge red flag that the main page doesn’t talk about what it contains, it just lists a bunch of things it doesn’t have. It’s also a huge red flag that they chose such an intentionally misleading name that is only one letter away from a real drug with peer-reviewed science backing it up.
I recommend stacking L-theanine with caffeine/coffee to prevent jitters. It’s why Green Tea has a more calming wakefulness than other sources of caffeine
https://www.healthline.com/health/l-theanine#benefits-and-uses