Researchers from the University of Calgary in Canada studied 647 children aged six months to five years who suffered with mild dehydration from gastroenteritis.
Half the kids were given half-strength apple juice followed by their favourite drink and the other half received an apple-flavoured electrolyte solution - which is the usual treatment for mild dehydration from gastroenteritis in kids.
They found 25% of the kids who drank the electrolyte solution still needed additional treatment, compared to only 17% of those who drank apple juice.
"These results challenge the recommendation to routinely administer electrolyte maintenance solution when stomach pains and diarrhoea begins," Study leader Dr Stephen Freedman said.
In the study, published in the Journal of the American Medical Association, children treated with apple juice also required fewer intravenous fluids (administered directly into their veins) and were less likely to need hospital treatment, than children given an electrolyte solution.
Electrolyte maintenance solution is "off-putting" for babies and toddlers because of the taste, Dr Freedman said.
"The use of dilute apple juice may be an appropriate alternative to electrolyte maintenance fluids in children with mild gastroenteritis and minimal dehydration," Dr Freedman continued.
Jenny Edelstein, a child nutritionist at Brain Food London said the findings could be "very useful" for parents.
"This new finding is not only very interesting from a medical perspective, but also has significant practical implications for parents," she told The Huffington Post UK.
"Young children can get dehydrated very quickly from gastroenteritis and this often leads to A&E visits.
"I hope this research will give parents a valuable tool for treating dehydration at home and avoiding the need for treatment in hospital.
"I would also recommend giving children diluted apple juice in case of tummy upsets when travelling."
Charlotte Stirling-Reed, child nutritionist at SR Nutrition believes more research is needed.
"This is an interesting and fairly large study looking at the effectiveness for hydration solutions for gastroenteritis - a common paediatric condition," she told HuffPost UK.
"It simply suggests that diluted apple juice may be an appropriate alternative to electrolyte solutions, however more research is needed and getting advice from a GP or medical professional is essential if a child is unwell.
"Fruit juice - if offered to young children - should be diluted and only offered with a meal to protect children's teeth."
Commenting on the study, the NHS stated: "This may not work for all children, as the study didn't include any babies under six months, children with more serious stomach upsets or other conditions, and those who were already severely dehydrated.
"The advice from the National Institute for Health and Care Excellence (NICE) is still to give your child rehydration solution if you're worried they may become dehydrated and to seek medical advice if they don't get better.
"Fruit juice could make their diarrhoea worse and the current advice is that it should be avoided."