What is the drink sold by the convenience store headquartered in Irving, Texas referred to in Oklahoma?
Slurpee:  In Oklahoma, they are known as "Icy Drink". 7-Eleven: 7-Eleven is an American-Japanese international chain of convenience stores, headquartered in Irving, Texas, that operates, franchises, and licenses some 56,600 stores in 18 countries.
"Icy Drink"