A recent survey by the Children's Food Campaign found the vast majority of public parks around the UK had no drinking fountains, putting health at risk.
"This encourages thirsty children to turn to sugary alternatives or go without, both of which are bad for their health," said campaign coordinator Christine Haigh.
The survey of 140 parks around revealed only one tenth had fountains, and in only two thirds of these parks were any of the fountains working.
Only eight parks, barely 6% of the survey, had every fountain working. Yet pollsters found most of people would happily use drinking fountains if they were available.
Haigh said: "Health professionals advise water is the best thing for thirsty children to drink yet we make it hard for them by failing to provide water fountains in parks.
"Drinking fountains are a cheap and easy way of improving public health. It's not rocket science - the Victorians were way ahead of us on this issue."
Christine Blower, general secretary of the National Union of Teachers, said:"It is tragic: even in the handful of parks that have drinking fountains so few work."
"Local authorities should commit themselves to installing and repairing drinking fountains in the interests of children's health."
Dr Vivienne Nathanson, head of science and ethics at the British Medical Association, said: "At a time when we are fighting an obesity crisis in the UK, it is essential children readily have access to free, safe drinking water in schools and public parks."
Professor Richard Parish, chief executive of the Royal Society for Public Health, said: "Access to clean water is essential: you cannot go wrong with water!"