Sour Strawberry -  Prepare for a flavor explosion with NKTR Sour Strawberry! The combination of a sweet, mature strawberry and acidity, which carries throughout, will make your taste buds blissful. NKTR Sour Strawberry is made with TFN ® Nicotine is the only genuine nicotine brand that is not derived from the leaf, stem or waste dust of tobacco. TFN ® Nicotine is odorless and tasteless while providing a purer and refined flavor profile.