A U.S. advocacy group has launched a class action lawsuit against Coca-Cola, alleging the soft drink giant is misleading consumers with its brand of VitaminWater drinks.

Coke, who owns VitaminWater's parent company, markets the colourful beverage as a healthy alternative to sugary soda dubbed "responsible hydration."

But the Center for Science in the Public Interest (CSPI) alleges that VitaminWater's sugar content make it anything but healthy.

"In fact, according to CSPI nutritionists, the 33 grams of sugar in each bottle of VitaminWater do more to promote obesity, diabetes, and other health problems," said the CSPI in a statement released Thursday.

"We want Coca Cola to stop selling these drinks as healthy drinks, they're just not," said senior CSPI nutritionist David Shardt in an interview with CTV News.

Shardt added that the suit also aims to reimburse "fooled" consumers.

In a release posted on their website, Coke called the suit "ridiculous" and "ludicrous."

Coke also said that labels clearly show the calorie content and noted that the suit is simply a public relations stunt aimed at garnering media attention.

"This is about grandstanding at a time when CSPI is receiving very little attention."

Claims are 'deceptive' and 'unsubstantiated'

Written on bottles of VitaminWater, a statement reads: "Legally, we are prohibited from making exaggerated claims about the potency of the nutrients in this bottle."

But the writing goes on: "Therefore, legally we wouldn't tell you that after drinking this, Eugene from Kansas started using horseshoes as a ThighMaster or that this drink gave Agnes from Delaware enough strength to bench press llamas."

While VitaminWater brass has said that much of their marketing is intended to be humorous, the CSPI says that such marketing claims are "deceptive" and "unsubstantiated."

VitaminWater comes in several different flavours, which are brightly-coloured and bear names like "defence," "restore" and "rescue."

On its website, VitaminWater states that each of its eight "grab-health-by-the-horns" varieties offer "a unique blend of nutrients to help you shine."

One variety, which is called "xxx," will help to "keep your insides clean, "according to the website, which lists the drink's flavour as "acai-blueberry-pomegrante (sic)."

But according to CSPI, the drink "has no blueberry, pomegranate, or acai juice."

The suit against Coca-Cola, which purchased VitaminWater's parent company Glaceau in 2007 for more than US$4 billion, was launched on Wednesday in the United States District Court in the Northern District of California.

The suit also lists California resident James Koh, who used to purchase VitaminWater after working out, as a plaintiff.

"When I bought VitaminWater, frankly I thought I was doing myself a favor health-wise," Koh said in a release.

"I was attracted by the prospect of getting extra vitamins. But I had no idea that I was actually getting almost a Coke's worth of sugar and calories. There's no way I would have spent money on that, had I known."

Each bottle of VitaminWater contains 33 grams of sugar. A can of Coke, though smaller by volume, has 42 grams.

In 2007, the CSPI sued Coca-Cola and its partner Nestle over a drink called Enviga, which the companies claim burns more calories than they actually contain, meaning drinking the tea-based beverage can result in weight loss.

According to the CSPI, those claims have not been supported by scientific studies into the drink.