The Food Standards Agency also reported that 'healthier' drinks, or those without high levels of fat or added sugar, were profitable for schools, triggering the launch of a new guide for schools on how to set up healthy vending machines.
The project, supported by the UK's Dairy Council, provides schools with practical and commercially sound advice on where best to locate the machines and what products to stock.
Twenty per cent of UK children are overweight and around 10 per cent are estimated to be obese, according to recent data, which has alarmed the government and prompted increasing scrutiny of the way schools and food companies are influencing children's diets.
Health concerns have already obliged food and drink manufacturers to curb the rate of new product development, according to Mintel's GNPD, which monitors product launches. A total of 543 new products or extensions targeted at kids were launched in 2001 by food and drink manufacturers, but this dropped to 366 in 2003 - and to just 46 in the first half of the current year.
Nevertheless British children aged 7-14 receive a massive £1.5 billion in pocket money each year, spending a large share of this on food and drink, shows Mintel research.
During the pilot vending machine study in 12 different schools in the UK, about 70,000 units of product were sold, with more than 35 per cent of these milk or milk products. And while two schools made a small loss, the rest were profitable including two that achieved profits of £863 and £1283 (over 18 and 24 weeks, respectively).
The FSA said: "If just one in five of the 5,000 plus secondary school headteachers in England and Wales placed a single healthier drinks machine into their school we would see approximately 14 million additional units of milk, milk products, pure juices and waters sold to children every year."
The new guide on vending machines is part of an action plan announced by the FSA in August designed to improve children's diets. Other initiatives will see the publication of nutritional criteria for the food industry (including the food service sector) with the aim of reducing levels of fat, sugar and salt in foods, product ranges, and meals aimed specifically at children.
The Agency will also publish best practice advice on signposting of foods, meals or snacks high in salt, sugar or fat, and of healthier options.