Well there
ejuice is at 4.2 mg/ml... 100 mg of caffeine is a standard for a coffee (is actually kind of weak).
So
vaping that straight would be hard to even get 1 cup of coffee worth of caffeine.
Unless there is some typo on there website, or vaped caffeine hits you differently than caffeine that is digested, like 20 times as effective vaped then it won't do much.
This is why there is doubts on caffeine working at all in an
ecig. I did pick up a 15 gram bag of there anhydrous caffeine to experiment with. I will make a thread if I ever have conclusive results.