One cup of coffee a day is an entire solution for my ADHD problem

I have some kind problems of poor focusing, agitation, forgetfulness and uncarefulness/impulsive decision which are main characteristics of ADHD. However, I don't have a hyperactivity problem, so my problem is called ADD which is  an ADHD derivative.

I've tried a lot methods to make my focusing better, here are the lists

• Combining alternate day fasting(IF 32/16) with HIIT
  • all of them increase BDNF which play a main role in brain neuroplasticity and neurogenesis(at hippocampus)
    • Fasting less than 20 hours in human doesn't increase BDNF, so I did fasting for longer time. 
    • HIIT releases BDNF 4-5 times more than normal exercise and also helps burn carbohydrate stored in the body which help release BDNF faster in fasting.
  • it improves my problem solving ability, faster reaction reflex. However, eating too much in one time causes the very heavy work load on my body to manage such a huge amount of nutrients which in the long term I think it may certainly have an effect on my metabolic health.(I may change back to the Time restricted fasting IF 18/6 and fasting all day sometimes)
• Meditation
  • for calming my mind and my emotion. It helps me so much more easier to be happy, detach from the world, but for focusing I am just a starter so I still didn't get much benefit on my focusing problem.
• vision therapy
• avoid light flickering

All of them does help but just indirectly and not have much direct effect to my focusing problem, my lack of focusing is still dominant and I still can't focusing at my reading and it still kept more deteriorating over time.

Then, I try drinking coffee again after stop drinking it for a while. It is so much different. My reading improves enormously from 30 minutes of maximum focus a day to 6-8 hours focusing which is around 12-16 times or 1200-1600% better!!!!

I find some information (and a little one here)tells that caffeine can act like stimulant drugs that use for treating ADHD (though it is less effective and everyone doesn't get the same effect.). 

• ADHD usually lack of dopamine which make them unable to focus at their daily routine or work and craving for thing that give them more dopamine artificially such as desserts, games, entertainments which all of them are procrastination.
• Caffeine do the same as stimulant drug in increasing dopamine helping ADHD focus better without procrastination

However, there is an evidence that drinking coffee in chronic lacking of sleep may make the grey matter of brain shrinking. So I decrease the amount of coffee daily intake and rely on exercise and fasting to increase brain cognitive function instead.