But more than 50% of manufacturers have changed their formulas to cut sugar, according to figures last month from the Treasury.
The Soft Drinks Industry Levy comes into effect today.
PepsiCo beverages, which are distributed by Britvic in the United Kingdom, will continue with the same recipes, with the costs passed on to the consumer.
As diet drinks are exempt from the tax, the recipes of Diet Coke and Coca-Cola Zero will remain the same - and the company are even increasing the bottle sizes of these brands. Consumers tell us not to change it and we believe they should be able to choose a Coca-Cola Classic if that's the drink they want.
"While the sugar tax may have pushed some brands to progress at speed, or make changes more publically, the movement towards healthier alternatives pre-dates the March 2016 budget".
The sugar tax adds 18p per litre on drinks that have a total sugar content of 5-8g per 100ml - a sugar content of 5-8%.
The sugar content of Sprite was cut by a whopping 50% a year ago.
A spokesman for the drink's maker A.G. Barr said: "Irn-Bru continues to be made using the same secret Irn-Bru flavour essence, but with less sugar".
Insight from our suppliers has suggested that products which contain the highest amounts of sugar could see a percentage increase for operators of up to 35%, albeit on low volume items. While the levy on high-sugar drinks is a response to the obesity crisis - 20% of children in the previous year of primary school in England are now obese - there is huge concern about children's teeth as well. "The levy is a ground-breaking policy that will help to reduce sugar intake".
In a bid to protect small businesses, the British government has also granted a reprieve to soft drink producers selling less than 1 million litres of product a year.
Malcolm Clark, policy manager at Cancer Research UK, said: "Even before its formal introduction the levy has already had a significant effect, encouraging numerous biggest companies to go further and faster in changing their recipes to reduce the sugar in their drinks".