Poppy pod tea all the way! J/K.
I like coca tea, yerba mate, and most kinds of green tea, like jasmine or pomegranate-flavored. White tea is also good, with a milder flavor and more antioxidants than green. I used to make my own teas out of loose oolong and green tea leaves and would make different preparations, like stimulating, relaxing, uplifting, etc. My relaxing one ("Twilight Dream") sold the most and had calming herbs like chamomile, valerian root, vanilla, ginger and cinnamon. It's fun to experiment with adding different herbs to your own tea, or just leaving it as an herbal tea with no caffeine. And there really is no reason to spend tons of money on those expensive preparations like "Sleepy Time" when you can just make your own for next to nothing.
The health properties of tea are pretty impressive. You can drink it hot or cold, add honey, milk or sugar, and customize it to your own taste. If you don't do well with caffeine, you could always go for decaf or try another stimulating tea like yerba mate or coca leaf. (Yerba has caffeine, but doesn't cause the unpleasant side effects of other caffeinated beverages.) It's milder than coffee and has lots of antioxidants, polyphenols and minerals which have been shown to help prevent a number of diseases from cancer to heart disease. Drink up!