If you want to add a nicotine content to your Double Brew shortfill it is easy to do. There is enough room left in the bottle for the addition of two 10ml nicotine shots, which are an unflavoured e-liquid used to add nicotine to shortfill bottles.
Adding two 18 mg/ml nicotine shots to a Double Brew shortfill will create 120ml of 3 mg/ml e-liquid, you can add less if you want a lower strength, but we do not recommend making your shortfill any stronger than a 6 mg/ml strength as this will dilute the flavour significantly. You just need to remove the cap and nozzle from the shortfill, empty the nicotine shots into the bottle, replace the nozzle and cap, and give it a good shake, then your e-liquid is ready to use.