The deals for this type of product positioning occur quite high up in the chain.
To give an example Yum! brands (KFC, Pizza Hut, Taco Bell, etc) was formed as a subsidiary of PepsiCo. Although PepsiCo has divested from Yum, their pre-existing relationship is why these restaurants only serve Pepsi's soft drinks.
Deal-making is also why you see patterns like this emerge in other places such as convenience stores that only sell beverages from the Coca-cola company (i.e. higher volume sales from just one supplier yields a better discount than splitting sales across multiple suppliers).
It's relatively rarer to see more than one beverage supplier at a restaurant, club or convenience outlet.
For convenience stores, particularly ones with few or no built-in wall coolers, the typical deal is the Coca-Cola or Pepsi distributor will provide and maintain a free-standing cooler, but it can only hold products from that distributor (often the distributor stocks it for you). Thus you'll typically see Coca-Cola and Pepsi products segregated in different coolers, if the store sells both.
I presume, but don't know first-hand, that for built-in coolers you want stocked by the distributor, they'll also require segregation. Frito-Lay distributors operate similarly--they'll come in and stock your shelf if you want (I dunno if there's a sales premium), but typically they'll require the Frito-Lay products be segregated, and they'll provide branded shelving if you want.
In my experience living here my entire life it’s _far_ more common for a restaurant/ fast food joint to have exclusive deals with one or the other.
That being said there is one popular gas station chain around here that historically sold Coke and Pepsi products in their fountains but in the past decade or so they’ve switched to exclusively Coke products in the fountains (but they still sell bottled Pepsi products)
To give an example Yum! brands (KFC, Pizza Hut, Taco Bell, etc) was formed as a subsidiary of PepsiCo. Although PepsiCo has divested from Yum, their pre-existing relationship is why these restaurants only serve Pepsi's soft drinks.
Deal-making is also why you see patterns like this emerge in other places such as convenience stores that only sell beverages from the Coca-cola company (i.e. higher volume sales from just one supplier yields a better discount than splitting sales across multiple suppliers). It's relatively rarer to see more than one beverage supplier at a restaurant, club or convenience outlet.