Following a trial in a handful of outlets, a forest fruits variety is rolling out to 600 Tesco stores. It joins the existing citrus and passion fruit & orange flavours.
The newcomer contains half the RDA of a range of B vitamins, including niacin and B6, which help reduce stress levels and increase energy. It also includes gingko, extracts of green tea and guarana.
The company said the variant was a response to shoppers wanting "to take the bore factor out of drinking the recommended two litres of water a day".
Since its launch in Tesco last May, the brand has achieved sales of £5m, the company said, with sales running 400% ahead of the original forecast.
It said other major retailers had expressed an interest.
"We will be disappointed if sales do not double over the next year, driven by distribution and consumer uptake," said managing director Chris Pomeroy.