Coca-Cola should not offer children sugary drinks as its festive truck visits Glasgow this weekend, according to an NHS chief.
Dr Linda de Caestecker urged the company to act responsibly and promote a healthy start.
She believes Coca-Cola should give out "sugar-free drinks and water" during its tour across the UK.
A Coca-Cola spokesman said two of the three drinks on offer from the truck were sugar free.
The truck will visit Silverburn Shopping Centre and Asda Robroyston this weekend.
Dr de Caestecker said the population was already consuming too much sugar and warned that drastic action was needed to tackle childhood obesity.
Latest figures show that almost one in five children are overweight or obese when they start primary school and almost one in three by the time they leave primary school, and Dr de Caestecker fears half of all children will be overweight or obese by 2020 unless action is taken.
She said: "There is a lot of excitement for children when the Coca-Cola festive truck visits towns up and down the country.
"This weekend the truck is visiting two venues in Glasgow and I am asking them to help us provide a healthy start for young children by only offering sugar-free drinks or water.
"We are asking Coca-Cola to stop promoting sugary drinks during the 'Happy Holidays' truck tour and only distribute sugar-free drinks and water to the general public, in particular to children.
"We ask that Coca-Cola takes responsibility as an influential brand and support customers to make healthier choices."
She said all commercial organisations could help tackle obesity and put to rest the myth that "sugar-free drinks are as bad or worse than sugary drinks".
She added: "Our population is already consuming too much sugar and a small can of standard Cola contains almost the maximum daily amount of sugar recommended for a small child.
"It is not, therefore, just a small festive treat but gives a very poor message to families."
Dr de Caestecker is calling on the parents of children and young people to offer their children only sugar-free drinks or water which she said was healthier and better for their teeth.
However, she said that many people, including public health officials, are concerned about the wider impacts of shifting consumption habits from sugary food and drinks to those that are artificially sweetened.
In a statement, Coca-Cola said: "The Coca-Cola Christmas truck tour provides a moment of fun for everyone in the build-up to Christmas and we've had a positive response from many people in Glasgow to the news that it will stop there this year.
"The truck tour is a one off, annual event where we offer people a choice of 150ml samples of Coca-Cola Classic, Coca-Cola Zero Sugar or Diet Coke - so two of the three options are no sugar drinks.
"We also have a policy of not providing drinks to children under the age of 12, unless their parent or guardian is present and says they can have one."