The methods of caffeine ingestion range from typical (coffee) to X-TREEM (energy drinks) to sort of hardcore (5-Hour Energy), but none have been outwardly juvenile—until now.
Each Nixie Tube packs 100mg of caffeine, about 20% more than a cup of coffee, and comes in colors and flavors a million percent less natural. They come in your standard candy flavors, from the classic lemon/lime to blue raspberry, which never has, never will, and does not now exist in the real world. They're available only from ThinkGeek (thank god; we don't need these becoming the new Jolt Cola) and cost $9 for five tubes. [ThinkGeek via CrunchGear]