Coca-Cola is reported to have lost 0.4% of market share to 43.7% last year, while sales fell 0.2%. PepsiCo gained 0.2% of market share to 31.6% and sales rose 1.3%.
PepsiCo has made many headlines recently including last week when it wrested the sponsorship of the US national football league from Coke for $160m (£111.3m).
It has also beaten Coke to the contract to supply United Airlines, the second largest airline in the US.
PepsiCo has also signed up high-profile celebrities Britney Spears, David Beckham and Pop Idol runner-up Gareth Gates to promote the brand.
Meanwhile, Coke is said to be rebuilding its central organisation which was stripped out during a restructuring in the mid-90s in order to distribute more power to local divisions.
Now it has been reported in two US magazines -- the Beverage Digest and the Atlanta Journal -- that it is planning a vanilla-flavoured Coke.
The company has declined to comment on the reports, but it is believed that a drinks company the size of Coke would take on the launch of a new brand with caution.
The last new flavour it introduced was Cherry Coke in 1985. The only change it has made to the brand since then was the disastrous relaunch of "New Coke" 16 years ago.
However, Coke's sponsorship of the winter Olympics appears to have bucked the brand's fortunes, while the launch of a lemon-flavoured Diet Coke is reported to have been received well in the US.
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