In the winter I boil a pot of tea made with lightly caffeinated Jasmine (my stomach can't tolerate heavy caffeine). Since the weather's turned hot, I have felt less inclined to consume steaming beverages in the middle of the day. So I've taken to making a concoction of iced Jasmine green tea, lemon juice, agave, and homemade raspberry juice. It's extremely refreshing and has that perfect little kick to spur on the writing process.
What is your favorite writing fuel?