Answers:
If you consider the "energy drinks" close to Red Bull, or No Fear as carbonated, they would rank the best around 75-80mg caffeine per 8 oz or so. In the soda category, Jolt has be king for years at 71mg per 12 oz. But really, you still can't beat espresso at 120mg per 1.5-2oz for the stimulation you really necessitate!
Other Answers:
I don't have a correct answer to this, but there is a drink call Bawls. I've included a link to it within the Sources section.
Source(s):
http://www.thinkgeek.com/caffeine/drinks/2818/
Carbonated drinks offer heaps with giant caffeine content. I would chalk it up to taste. Which one would you want to drink?
Jolt
Mountain Dew
Red Bull
Source(s):
http://www.cspinet.org/new/cafchart.htm
I agree beside One from above. JOLT. Like the drink says "twice the caffiene and adjectives the sugar".
Source(s):
Partaken in it's effects oodles times when I needed to study after partying too much.