Many popular children's lunch box juices contain more sugar than Coca-Cola and parents should steer clear of them, health groups say.
The Obesity Policy Coalition is warning parents that with the school holidays ending, they should not assume products like juice are healthy just because of claims that they have "less sugar" or are "free from artificial colours and flavours".
The group's analysis of the lunch-box size poppers has found many have the equivalent of five or more teaspoons of sugar in them, with several containing even more sugar than the same size serving of Coca-Cola.
The worse offender is Golden Circle's Sunshine Punch poppers, which its website describes as "perfect to fit in a school lunch box". However, it has more than 30 grams of sugar per serve, or the equivalent of 7.7 teaspoons.
Obesity Policy Coalition executive manager Jane Martin said parents could be forgiven for thinking fruit drinks were healthy.
"I've just been in the supermarket and they are all packaged up and discounted for 'back to school'," she said. "I used to put them in my kids' lunch boxes because they are very convenient and you think it's good for them.
"Most parents wouldn't dream of putting soft drinks in their kids' lunch boxes, yet many of these drinks are just as high in sugar or even worse."
Australia's dietary guidelines say that while fruit juice can be a source of vitamins, people are better off getting those vitamins from pieces of fruit.
"The occasional use of fruit juice may assist with nutrient intake when fresh, frozen or tinned fruit supply is suboptimal," they say. "Fruit juice is energy-dense and if consumed in excess, it can displace other nutritious foods from the diet and may lead to problems such as obesity."
Queensland University of Technology professor Amanda Lee, who chaired the National Health and Medical Research Council committee that developed the guidelines, said there was increasing evidence that our bodies didn't register energy consumed through drinks, and so kilojoules we drank in things like fruit drink would come on top of the rest of our energy intake.
"The major issue with fruit juice is it is associated with increased risk of weight gain in children and adults, increased risk of dental caries, and there is a concern that it displaces milk in the diets of children and infants," she said.
"There's also a particular problem in hot climates with children doing sport, because when you are a little bit dehydrated it increases the strength of acid in the saliva.
"You can get quite striking and rapid deterioration of the enamel."
The guidelines recommend that children aged under 12 months don't drink any juice, yet data indicates 89 per cent of them do so.
Professor Lee said there should be no confusion about what foods were healthy.
"The Australian dietary guidelines spell out a wide range of culturally appropriate products," she said. "Unfortunately, it's not as heavily promoted because no one makes a buck out of it."
Ms Martin said if people did give their children juice, it should only be occasionally; it should be 100 per cent juice, and should be only about half a cup in size.
"What is recommended for kids is low-fat milk, water and whole fruit," she said.
Ms Martin said many of the drinks were packaged to look more healthy, with images of real fruit and claims about being a good source of vitamins.
Some, such as Pop Tops fruit drink, which claims to be perfectly designed for children and their "small hands", prominently promote they have "30 per cent less sugar" and no artificial sweeteners, yet also have more sugar than the same size serving of Coca-Cola, at 27.5 grams for the orange flavour.
"The reality is these drinks just aren't a healthy choice," she said.