The National Addiction Centre is calling for an excise tax to be introduced on fizzy drinks to stop people becoming addicted to them.
It follows an inquest into the death of Invercargill woman Natasha Harris, which heard that she was addicted to Coca-Cola and drank up to 10 litres of it a day.
National Addiction Centre director Doug Sellman says companies are promoting fizzy drinks as harmless.
He says an excise tax needs to be introduced to soft drinks, to warn people that it could have health effects.
Her family says soft drinks need warning labels of the potential harm.
A pathologist, Dr Dan Mornin, who carried out the post-mortem, says she died from cardiac arrhythmia, which is when a person's heart beats irregularly.
When she died she had no teeth, vomit in her airways and gallstone disease, he says.
Ms Harris's partner, Christopher Hodgkinson, says she was addicted to Coca-Cola and would drink nearly 10 litres of it daily.
She would suffer from withdrawal symptoms and had poor health in the months leading up to her death.
Mr Hodgkinson's mother, Vivean Hodgkinson, told the inquest that soft drinks need labels that warn of their harm.
Another pathologist, Dr Martin Sage, told the coroner that consuming litres of caffeine drinks excessively over a long period, could potentially result in death.