was to drink mate tea.
South Americans (especially in Southern part; Argentina, Paraguay, Uruguay and so forth) drink mate religiously.
They would bring a huge cop filled with yerba leaves, which accompany
silver straw to drink the tea. Of course, people would refill the cop as much as they would at any given time of the day.
Back in Japan, I do not use the same equipment as they do, but I do drink the same leaves as much as enjoy Japanese or English tea. The study says that mate contains no caffeine and has lots of minerals.
Drink mate, and be happy!