ja not a good idea...check this link out..they selling nicotine free caffeine loaded vape pens in the US...scary reading
http://m.huffpost.com/us/entry/us_55c8c514e4b0f1cbf1e5a202
Good lord that is scary, and on a cigalike too. I have witnessed someone having a caffeine overdose (too many red bulls in too short a time) To the point we had to rush her to the ER. Luckily she was fine but it was a real eye opener.
vaping it is a bit of a step too far IMHO especially in the world of sub-ohm vaping and 200+ watt mods. Asking for trouble if you ask me.