parents who would not dream of giving their children Coca-Cola might be packing their lunchboxes with juices that are even more sugary.
Action on Sugar surveyed more than 200 juices, smoothies and fruit drinks to find more than a quarter had the same level of sugar or more as Coke, which has 10.6g per 100ml.
Among the worst offenders identified by the Queen Mary University of London-based campaign group were Asda's Chosen by Kids Tropical Juice From Concentrate, which contains 13g of sugar per 100ml, and Tesco Goodness Slurper Apple & Banana Fruit Smoothie Snack for Kids, which contains 16.1g of sugar.
Action on Sugar nutritionist Kawther Hashem said it was a concerning finding, given childhood obesity and tooth decay.
Fresh fruit juices tended to do better than fruit drinks or juices made from concentrate, she said, but warned parents against seeing the word "juice" on a label as a green light.
"It wasn't clear-cut, but I do think the ones at the top of the sugar list are usually from concentrate," she said.
Parents were better off giving their children diluted juice or water and a piece of fruit.
Ms Hashem also recommended parents steer clear of artificially-sweetened drinks.
"These are young children," she said. "You're training their taste buds - give a child an orange rather than something that tastes like orange."