The impulse formats are currently available in 500ml bottles, but Britvic which owns the Tango brand and bottles PepsiCo's Pepsi and 7Up under an exclusive bottling agreement is switching the drinks to larger bottles to improve their value-for-money credentials and provide shoppers with a bigger on-the-go format.
The bigger bottles, which are due to roll out in April, would still carry the current 500ml price tag of 99p and would rejuvenate category sales, Britvic predicted.
The £2.2bn carbonates category has grown 5.5% over the past year but, according to Britvic, all of the growth has come from the multiples, where sales have risen 9.2%. Sales in the convenience and impulse channel, however, are in long-term decline down 2.6% over 2009 following a 3.4% dip in 2008.
Noel Clarke, senior brand manager for Pepsi, said the weak performance in on-the-go was down to the recession as well as "the fact that there has been no new news or significant pack innovation in the on-the-go carbonates market in over 15 years", when the 500ml bottle was first launched.
"These issues have resulted in a situation where more than 82% of UK households purchase carbonates in a multiple grocer each year, but only 44% purchase in the on-the-go channel," said Clarke. "Closing this gap represents a £40m opportunity for on-the-go retailers."
He predicted the bigger bottles would be more attractive to consumers who wanted a drink they could buy at lunchtime and drink throughout the afternoon.
"There are no other carbonates available in 600ml. We looked at a series of different sizes, but 600ml was perfect for portability."
The launch will be supported by a £5m marketing above-the-line campaign, starting on 12 April.
The news comes two weeks after Pepsi's new-look packaging and logo arrived on shelves. The design was introduced to the US in February last year, and is gradually being rolled out across the globe.