It's a Kiwi thing, adding a shot of raspberry syrup to a Coke or Lemonade. The kid's cocktail, a favourite of university students, is a spur-of-the moment mix at the soft-drink stand at Burger King.

Well, that tiny bit of innovation has paid off. The keepers of the giant Coca Cola brand at the company's Atlanta headquarters have taken notice -and we'll drink it here first.

New Zealanders will become the global guinea-pigs for Raspberry Coke from June 1. The limited-edition flavour was a local idea, but Coca Cola's New Zealand team did not have to look far for inspiration.

"We observed the behaviour at self-serve soda fountains where consumers can make the choice themselves. Coke and raspberry is by far the favoured combination," Coca Cola New Zealand manager Gareth Edgecombe said.

Taking the cautious approach, a range of flavours was tested with Coca Cola. "Raspberry went through the roof."

That made it an easy sell when the New Zealand team took it to head office, where management are constantly inundated with fresh ideas. "The fact that the raspberry experience was already occurring in-market and that the New Zealand market accepts innovation - it was a convincing story," said Edgecombe. "We were able to take these insights and the New Zealand context and become a global leader."

Raspberry Coke is the first flavoured Coca Cola to debut in New Zealand. Its longevity in this market will be assessed on the numbers and its popularity is likely to play a key part in whether Coca Cola executives in Atlanta decide to introduce it elsewhere. Edgecombe said testing in New Zealand made a lot of sense. Although a small market, New Zealand had all the elements of larger Western markets.

New Zealanders also had a strong affinity for the Coca Cola brand and were known as early adopters of new products, he said.

But Raspberry is still just the third flavour that has been added to original Coke in New Zealand. Vanilla Coke, introduced in 2002, is still popular but Cherry Coke, released in the 1990s, did not stay the course. Both of those originated overseas.

Diet Coke drinkers had seen more options, with lemon, vanilla and lime flavours all introduced, lime just last year. Only lemon has disappeared.

Diet Raspberry Coke will also debut at the same time as the original version for the first time. Edgecombe said the fact that new flavours helped to draw converts to Diet Coke also played a part in that decision.

But it was also a nod to growing obesity concerns, concerns he believes will see Diet Coke become a bigger player than original Coke.

"We see Diet Coke as a real engine. It has the potential to be the biggest part of the franchise. At the moment, Diet Coke makes up 26 per cent of the total franchise - in the long term we see growth in Diet Coke potential the larger of the two."

Secrecy still surrounds Coke's plans on the advertising front. All Edgecombe would say was that the new drinks will be promoted equally through several channels, including television, with Coke's regular agency Publicis Mojo leading the campaign.

DesignWorks designed the packaging with Coca Cola's global design team. Advertising and design, along with all elements of the launch, may be considered for international use should Raspberry Coke go global. Sarena Saunders, a lecturer at Victoria University's school of marketing and international business, said the new flavour sounded like a good idea.

"It always staggers me when I go to Burger King, watching people make Raspberry Coke," she said. Given the new flavour did not diminish people's ability to choose original Coke, and the company was not replacing anything fundamental, it was unlikely to have any major impact on the brand should it fail. Nor were manufacturing costs for such a small change likely to be high, the main cost being promotion. Saunders said additions to existing product lines like a new flavour of Coke made up 26 per cent of all new products. New products that made it to market had a failure rate of 35 per cent to 50 per cent, the main reason for failure poor marketing.