So, this is all based on "averages" and such.

While the "lethal dose" of caffeine is "estimated" at between 150 and 200 mg per kg of body weight[^1], the empirical evidence points to the possibility of death with much lower doses: a death with a dose between 3 and 6 mg per kg of body weight has been observed in 2017. However, this is a very broad estimate, based the reported consumption of a precisely unknown quantity of beverages from undisclosed brands... In this case, the individual was also clinically obese at the age of 16, so it is fair to speculate that he never really exercised, and that he had a rather high amount of visceral fat, along with an underdeveloped cardiac muscle.

All this to say that we do not have precise empirical data, nor thorough clinical studies, to exactly estimate the lethal dose of caffeine for humans.

However, we do know that consuming water, or any liquid, can be fatal, with doses as low as 8L over a few hours[^2]. There has been other reports of people dying drinking 11L[^3].

So this was obviously meant in jest, I would not recommend drinking more than a couple coffees a day, and if you do, I would highly recommend to eat healthy, keep hydrated, and regularly exercise.

[^1]: The clinical toxicology of caffeine: A review and case study; section 7.2. — Estimated pharmacokinetics.
[^2]: Fatal water intoxication.
[^3]: YouTube — Chubbyemu, A Mom Drank 3 Gallons Water In 2 Hours. This is What Happened to Her Brain.