What’s the easiest way to refill?

I've been thinking about doing a guide for that on here, but haven't got to it yet. However, there's a YouTube video showing you exactly what you need to know.

GEEK BAR vapejuice refill hack - YouTube

It can be done by just popping off the mouthpiece, but then you can't tell exactly how full it is. From my experience, about a third of a 30ml bottle of vape juice (about 10ml) will do the job.

To remove the mouthpiece, I just grab it with a pair of pliers and give it a good twist. It'll pop right off, but note that it's got a vertical key on one side that has to be lined up so it won't go on correctly if you get it reversed.