The Director of Human Health at Safefood has said hidden sugars in common fruit drinks are contributing to childhood obesity.
Speaking on RTÉ's Morning Ireland, Dr Cliodhna Foley Nolan said that many parents hold the view that words like "juice" or "fruit" on drinks labels suggest that the drink contains little calories.
However, she said drinks such as "those that say 'high-fruit', 'ready-to-drink' or smoothies have a wide range of sugar content in them".
Dr Foley-Nolan was speaking as Safefood has produced an info-graphic identifying how much sugar is in sweetened drinks.
She is advising parents that eating the fruit instead of drinking its juice would be healthier for children.
"A small quantity of juice - in fact it's recommended that only 100mls, which is a third of a can of juice, is what's recommended for children per day because of the sugar content - infinitely more sugary than eating a whole apple, so really the logic is to have a satsuma or some grapes instead of the juice," she said.
Dr Foley-Nolan also warned parents that fruit drinks could be contributing to childhood obesity.
She said: "There really is clear evidence from numerous pieces of research that there are links between the consumption of sugar sweetened drink and overweight and obesity in children.
"And actually what's somewhat reassuring is that reducing their intake will help the child become a healthier weight. So I suppose what we're saying to parents is water, really, on a daily basis is the way to go."
Safefood said that many of the drinks it compared contained as much sugar as fizzy drinks.
For example, a 200ml serving of a popular juice drink contained 20g of sugar, which compared with 21.2g of sugar in Coca-Cola and Pepsi and 22.4g of sugar in 7Up.
The agency said some popular supermarket brands of cordials and dilutes had even higher sugar levels, with as much as five cubes of sugar in a small glass.
Obesity Specialist with the HSE Professor Donal O'Shea said there is clear evidence that "links the consumption of sugar-sweetened drinks to overweight and obesity among children and adolescents".
He said parents need to start viewing these drinks as "threats not treats" and not something to be had every day.
Prof O'Shea said milk or water were better options for children.