Green tea fan here as well! I've recently been a lot into Hojicha and Kukicha, two sorts of lower grade Japanese green tea, which have virtually no caffeine, so you can drink a lot without getting all jumpy. When I need something that gives me a bit of a caffeine kick I reach for Da Hong Pao, which is a very high-quality sort of Oolong tea from the Wuji mountains (China). But I like to change a lot and taste new types of tea. Green tea is indeed very ritualistic, and you need to know how to prepare each sort, because temperature, vessel type and time are essential to get the full flavour.
Regarding food. I don't eat in the studio, especially not in front of the computer. But I take a snack break once in the morning and once in the afternoon and mostly eat fresh fruit (whatever is around in the season... or whatever I can get in winter time)
edit: but I should add that most of the time I don't do sound work, since my main activity is being a graphic designer, and sound work is being pushed late into the evenings as of lately. But I think the principles is still valid.