A nutrition advocacy group on Thursday sued the Coca-Cola Co., the biggest beverage maker in the world, over what it calls “deceptive” health claims about VitaminWater.

The Washington-based Center for Science in the Public Interest accuses Coke of selling what it says is basically sugar water by claiming it has vitamins that boost immunity and reduce the risk of disease.

The group said the health benefit claims that Coca-Cola makes about its VitaminWater are “nonsense.” It filed a class action lawsuit in U.S. District Court in the Northern District of California.

“Any nonsensical claim you like, you can find in their line of VitaminWater,” said the group’s senior nutritionist, David Schardt. VitaminWater flavors are marketed with words such as defense, rescue, energy and endurance. The drinks’ top three ingredients are water, cane sugar and crystalline fructose, a form of sugar, according to the bottle labels. The 20-ounce bottle has roughly 33 grams of sugar, compared with about 39 grams in a typical 12-ounce soft drink.

Coca-Cola bought Glaceau’s VitaminWater for $4.1 billion in June 2007. It was considered a coup at a time when consumers were buying less and less soda. Consumers worried about their health had been driving down sales for soft drinks and switching to bottled water and other drinks like VitaminWater. The lawsuit says Coca-Cola “profited enormously” from sales driven by consumers’ health concerns.

“It truly shocks the conscience that a company like Coke would try to keep customers by selling them a soft drink and telling them it’s a vitamin,” said Stephen Gardner, director of litigation for the group. The lead plaintiff in the case, San Francisco resident James Koh, said in a statement, “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.”

“This is a ridiculous and ludicrous lawsuit,” Coca-Cola spokeswoman Diana Garza Ciarlante said. She called the lawsuit a “cheap, opportunistic publicity stunt.”

“Not only that, consumers can readily see the nutrition facts panels on every bottle of GlacDeau VitaminWater, which show what’s in our product and what’s not,” she said.

This is the second lawsuit the Center for Science in the Public Interest has filed against Coca-Cola. In 2007, the nonprofit sued Coke and NestlDe over claims that their artificially sweetened green-tea drink Enviga would help you lose weight. Also, it sued MillerCoors last fall to stop the brewer from selling Sparks, an alcoholic energy drink. Last month the company agreed to remove some stimulants from its formula.

The U.S. Food and Drug Administration warned Coca-Cola Co., the world’s largest soft-drink maker, that its claims that Diet Coke Plus contains vitamins and minerals violate federal regulations.

The agency said the company product is misbranded, because it includes the content claim “plus,” and it urged Coca-Cola to “take prompt action to correct these violations,” according to the FDAs Web site. Coca-Cola disputed the finding, saying the complaint doesn’t involve health or safety issues, according to the news agency.

The FDA letter said it was not appropriate to fortify snack foods such as carbonated beverages. Diet Coke Plus has vitamins and minerals, including 10 percent of the recommended daily value for magnesium and 15 percent for vitamin B-12.

A company spokesman said the label on Diet Coke Plus complies with FDA policies and regulations and that it plans to reply in detail to the complaint in early January, Bloomberg reported.

The FDA has begun cracking down on companies that overstate the benefits of the products. It has endorsed health claims on several foods, but only after government researchers verified that the products help prevent disease.

It is not uncommong for the FDA to send warning letters to companies that don’t follow regulations for manufacturing and marketing. The letters are not legally binding, but the agency can take companies to court if they are ignored.