You have to know what's your starting materials even b4 thinking of DIY.hmmm.. but DIY liquids, is there ways to include nic inside?
By that statement, I assume you're using zero-nic juice.
If that's the case, the only feasible way to 'Nicofy' your juice is to add flavorless nic juice.
But we shall not discuss this or another alternative methods further;
In case we infringe any rules in the heat of discussion....