Coca-Cola is planning to use smaller bottles and sell at a higher price in response to the upcoming sugar tax in March. In contrast to its beverage rival, Irn-Bru has decided to reformulate its recipe to reduce the sugar content and navigate around the tax.

Plans will see a 1.75-litre bottle of Coca-Cola shrink to 1.5-litre, but at the same time increase in cost by more than 10 per cent, rising from £1.79 ($2.43) to £1.99 ($2.70). The 50cl bottles will remain the same size but will increase in price from £1.09 ($1.48) to £1.25 ($1.70), representing a 25 per cent price increase in a matter of months, as they were available for just £1 ($1.36) until autumn of last year.

Conversely, AG Barr – makers of Irn-Bru – has made the opposite decision and will soon be bottling a revised version of the beverage, which will contain half as much sugar as the previous recipe due to the introduction of low calorie sweeteners, such as aspartame.

Announced in 2016, the sugar tax was designed to combat childhood obesity and stated that soft drinks manufacturers will be taxed at 18p per litre on drinks containing 5g of sugar or more per 10cl or 24p p/l if the drink has 8g or more of sugar per 10cl. The tax will apply to one in five drinks sold in the UK.

Coca-Cola Classic, which contains 10.6g of sugar per 10cl, will fall into the higher tax band, while the new Irn-Bru formula, with four rather than 8.5 teaspoons of sugar per can, will be exempt.

While Coca-Cola is willing to alter the recipes of other big brands in its portfolio, such as Sprite, Fanta and Dr Pepper, it is reluctant to change Coca-Cola’s ingredients following the infamous recipe change in 1985. AG Barr is optimistic, however, following its approach to deal with the sugar tax, stating that nine out of 10 taste testers were unable to distinguish a difference.