I dunno, I've never met anyone IRL who preferred Pepsi over Coke. At restaurants and cafés or wherever everyone would always ask for a coke, sometimes being met with "is Pepsi okay?".
No, it wasn't okay!
Well I must suggest taking a look at Middle East and the Indian Sub-Continent where Pepsi dominates.
And when I say Middle East, it is the oil-rich GCC (namely Bahrain, Kuwait, Oman, Qatar, Saudi Arabia, and the United Arab Emirates) and not the war-torn areas of Iraq & Afghanistan.
Trust me, I have had so many people assume that Middle East means Iraq-Afghanistan or Israel-Palestine-Jordan-Syria etc...
But that being said, Coco-Cola has more global coverage than Pepsi.
As it was the US Army's official drink back in the days during the WW1 and WW2.