AFAIK, there's only been one recorded death from lethal tea poisoning. I think it was something like 14 liters a day.

200 cups a day can be lethal, but the water poisoning will probably get you first.

The real dangers are alcohol + caffeine (the caffeine stops you getting tired, so you can drink more), or caffeine powder (one spoon can kill you).

Several liters probably isn't healthy though.

The headline is pure hyperbole. He thinks he has a problem because he gets a fuzzy head when he doesn't drink his tea. That's caffeine withdrawal.

I ruled out caffeine addiction already, it's the sugar.

I would really encourage you to revisit that assumption. I'm sorry to challenge you on this, but unless the tea you drink has very low levels of caffeine, you are ingesting quite a bit of the drug each day, levels that would cause dependency and addiction. The fuzzy head thing is a typical description of caffeine withdrawal.

Why do you think otherwise?

There are many kinds of tea, some with more, some with less caffeine. For a lark I finally tried the lightest in caffeine tea that there is: hot water. And as long as the sugar was there the same kick was present. As far as the science of it is concerned, I have no clue what the exact pathways are but the effect is tangible enough that I think I can rule out psychosomatic effects as well, though it is always hard to be 100% sure of this.

Best of luck to you regardless. My opinion would be hard to change on this issue without really exploring the details your caffeine consumption and the particulars of how you became convinced that that's not what it is. I don't want to badger you about it. Maybe just file this thought away somewhere. Caffeine is a drug, and you may be ingesting large quantities of it daily. That will affect you.