I believe their point is that it is possible to consume over a gallon of {liquid} per day, and as someone who used to drink unhealthy amounts of soda, I promise

I believe their point is that it is possible to consume over a gallon of {liquid} per day, and as someone who used to drink unhealthy amounts of soda, I promise it is possible to do it with even sugary, fizzy beverages let alone tea. Caffeine also has addictive properties which can override rational thoughts.