A Government department has told the manufacturer of a hydration drink consumed by top athletes, including America's Cup sailors, that it must add more sugar.

The Ministry for Primary Industries has given SOS, a powdered drink that mixes with water, until August 31, 2017 to add five times as much sugar to its formula to comply with the Australian and New Zealand Food Standards Code - otherwise it must remove any reference to the product hydrating or being an electrolyte drink.

In a letter to SOS Hydration in February, MPI said "a food sold as an electrolyte drink base must contain no less than 50g/L and no more than 100g/L of various sugars". SOS Hydration only contained 10g/L.

But the stance has been criticised by health agencies who are fighting for drinks to have less sugar them.

SOS director Tom Mayo said the Australian New Zealand Food Standards Code was based on "discredited science" and the drink did not need high levels of sugar to provide hydration.

The product was used by a raft of top athletes - many who are shareholders - including Team New Zealand's Peter Burling and Blair Tuke, British competitor Sir Ben Ainslie and the Artemis Racing Team.

Kiwis Scott Dixon and Nick Willis were also supporters.

Mayo said the company would remove the words "to treat hydration" from its packaging to comply with the code, but said it was difficult to explain what it was used for without those words.

The new packaging would read, SOS Drink Mix designed for athletes and everyday persons.

"That's where we are stuck as a young innovative company with some of the best athletes and investors behind us - we can't say a thing. There has been no innovation in this space in New Zealand for a long time... it's crippling business and it's hurting the population."

Mayo said New Zealand and Australia - who both follow the Australian and New Zealand Food Standards Code - needed to use the World Health Organisation Oral Rehydration Standards which acknowledged high levels of sugar were no longer needed for hydration.

An MPI spokesperson said it was the agency's role to implement the code and it started investigating the product after receiving a complaint in July.

According to the code, an electrolyte drink needed to have the right amount and types of sugar present to hasten rehydration, the spokesperson said.

MPI said it had been working with SOS to help it comply within the time frame and said anyone could apply to Food Standards Australia and New Zealand to change the code. The company could also prove the hydration claim for their food product.

Food Standards Australia and New Zealand spokesperson Lorraine Haase said the WHO Oral Rehydration Solution guidelines did not have the same purpose as electrolyte drinks and were used for therapeutic purposes such as treating diarrhoea.

"Electrolyte drinks have a different purpose and in the code are defined as for the rapid replacement of fluid, carbohydrates, electrolytes and minerals. This is why there is a minimum carbohydrate level set in the code," she said.

Dietitian Rebecca Moulds, who also plays for the Tactix netball team, said they used SOS for pre-games to keep them hydrated when they did not need the carbohydrates.

Moulds said she viewed electrolytes as being sodium, potassium and magnesium rather than carbohydrates so thought SOS should be classed as an electrolyte drink.

"I wouldn't be using SOS as a carbohydrate source during exercise, but it can be used as an electrolyte source."

New Zealand Medical Association president Dr Kate Baddock said New Zealand needed to look at reviewing the rules if it was out of line with international standards.

"You definitely don't need sugar to hydrate you. This is to do with recovery of expenditure during exercise. As an energy replacement following vigorous exercise then you do need some sugar."

Top sports players at Aorere College in Papatoetoe had been using SOS since January after looking for different drinks with less sugar given the obesity issue facing the South Auckland community.

Director of rugby Graeme Phillips said the school made up the drink for students and had eliminated the need for students to buy more sugary sports drinks after a game.

"I just find it really strange that a product with a lower sugar content can't be marketed as doing that job (hydrating) when it does," he said.

Cancer Society of New Zealand national health promotion and campaigns manager Shayne Nahu said people were drinking sports drinks thinking they were healthier than traditional fizzy drinks and this could contribute to weight gain.

He said unless you were a high performance athlete undertaking sustained physical activity then water was healthiest and best drink option."

Former triathlete Hamish Carter, who is a shareholder in SOS, said he was surprised by the amount of sugar required to be in a sports drink. He believed a debate needed to be had.

NZ Beverage Council president Olly Munro said its members were always looking at ways to reduce sugar and so "it seems crazy to be telling someone to increase the amount of sugar just so it can be classified as an electrolyte drink".