Coke Zero, the latest offering from US soft-drink giant Coca-Cola, has come under attack for failing to adapt to market trends and for potentially diluting the brand.
The no-sugar fizzy drink goes on sale in Britain tomorrow, backed by a reported £8m marketing budget.
The company is billing Coke Zero as its first brand launch since Diet Coke was introduced 22 years ago. Drinks such as Cherry Coke were not brands in their own right, merely "flavour variants", many of them limited editions, it said.
Stuart Whitwell, a joint managing director of brand consultancy Intangible Business, said Coca-Cola was being "far too optimistic" about its new drink.
"They are trying to buck a trend that's moving away from carbonated soft drinks. People want fruit juices, water, natural ingredients. And if it does work, it risks encroaching on Diet Coke. It's also just more confusion for the consumer and I think they have got it wrong."
But a Coca-Cola spokes- woman said the drink had a clear audience as it was aimed at men - it has been dubbed "bloke Coke" - instead of the mostly female Diet Coke drinkers. And unlike Diet Coke, it is supposed to taste like regular Coke.
"There's a place for all sorts of products and drinks throughout the day, whether that's juice in the morning, a cup of tea, a carbonated soft drink or an energy drink after the gym," she said.