Vitex

Vitex was a health drink developed by Pete Tyler.

Pete kept bottles of the juice in the flat at the Powell Estate, which Rose pointed out to the Ninth Doctor when they visited the flat during the alternative timeline created when Rose saved her father from being hit by a car. Jackie described it as tonic water. (TV: Father's Day)

Though nothing came from it in the main universe, in a parallel world it became extremely successful and made Pete a millionaire. The Vitex company was bought by Cybus Industries at some point in 2005. Their slogan was "Trust me on this." After the President of Great Britain commented that it tasted like pop, Pete told him it actually was pop. (TV: Rise of the Cyberman)

Behind the scenes
According to the book The Time Traveller's Almanac each flavour of Vitex was advertised to have various beneficial properties to the human body.

The flavours and properties were:
 * Cherry - reduces Wrinkles.
 * Pineapple - probiotic; prevents Hair Loss.
 * Sunrise (berries) - antioxidants; lengthens Life.
 * Violet (blackcurrant) - melts fat; vitamin C Boost.
 * Water lite - plain water with additives.