I have a slight suspicion that every time I consume something with caffeine it has a specific effect on me.

A good cup of black or green tea: Slight headaches at some times.
A cup of coffee (from work coffee machine): Depending on strenght slight attention issues or headaches.
A cup of coffee from a coffee shop which roasts its own coffee: One time a bit of stronger attention issues than the work coffee.

I usually notice it right away after consuming.
But I also have a very strong issue with staying hydrated.
Usually drink 0.5-1l per day until I notice the usual dehydrated-headache or when I am really focused and loosing it at times.
Usually it’s less prevelant at evening/night times.