X-Drinks are a type of
tasty stimulant beverage. It is produced by a
company called XTZ, which makes (to my knowledge) tea and soda. A distributor of said
beverages is
thinkgeek.com, which sells an assortment of the sodas in
boxes containing 24 bottles each.
There are 4 flavors of soda offered - root beer, cola, citrus, and berry. As ThinkGeek says, "These drinks each contain the maximum amount of caffeine (70mg per 12 ounce serving).They also contain Guarana(stimulant), Mate(stimulant), Betel Nut(stimulant), Kola Nut(stimulant, flavoring), Ginkgo Biloba(circulation), Korean Ginseng(digestive aid), Kava Kava (balancing)."
In my opinion, these are a nice investment for a sleepy geek, almost as good as regular sleep. The sodas taste nice, but they are slightly different from normal varieties. They taste best chilled. If you can't get them chilled, drink them warm from the bottle, because they taste terrible when poured over ice.
Also, try drinking your first one in the early afternoon to see how they affect you. Even if you have a tolerance for caffeine, they can still keep you awake much longer than you're used to. And don't exercise soon after having one.