Ejuice or Eliquid used to produce vapor in electronic cigarettes are widely sold both as separate bottled products, for use with refillable cartridges, and as pre-filled disposable cartridges. 

Contents of ejuice solutions vary, but their common aspects include water and flavorings in a propylene glycol or glycerin base. Nicotine is also included in solutions intended to fulfill a nicotine replacement role.

Hundreds of different flavor varieties are available. Some attempt to resemble traditional cigarette types, such as regular tobacco and mint, and some even claim to mimic specific cigarette brands, such as Marlboro or Camel. A wide variety of food flavors are also sold, from the traditional (apple, coffee, cappuccino) to the more exotic (chocolate, vitamin, Tutti Fruit).

Nicotine ejuice solution containing nicotine are available in differing nicotine concentrations to suit user preference. Dosing nomenclatures are not standardized and vary by manufacturer, but tend towards the following rough figures:

Ejuice said to contain low doses of nicotine tend to correspond to a nicotine concentration of 6–8 mg/ml.
Medium doses tend to correspond to a nicotine concentration of 12–14 mg/ml.
High doses tend to correspond to a nicotine concentration of 16–18 mg/ml.
Extra-high doses tend to correspond to a nicotine concentration of 24–36 mg/ml.
 
Flavors and nicotine are dissolved in hygroscopic components, which turn the water in the solution into a smoke-like vapor when heated. Commonly used hygroscopic components include propylene glycol, vegetable glycerin, and polyethylene glycol 400 (often sold under the abbreviations PG, VG, and PEG 400, respectively).

All three liquid bases are common food additives used in a variety of pharmaceutical formulations. Propylene glycol, the current dominating liquid base, has been utilized in asthma inhalers and nebulizers, and because of its water-retaining properties, is the compound of choice for delivering atomized medication. The FDA includes propylene glycol on its list of substances Generally Recognized as Safe (GRAS), and it meets the requirements of acceptable compounds within Title 21 of the Code of Federal Regulations.