Pop vs Coke. What do you call it?

In an ongoing debate between me, my brother and his wife, I was finally proved wrong about the regional name choice of a carbonated beverage.

My sister in law calls it soda, but we told her that only people from up north call it that (and thusly entirely discounted her opinion). I call it Coke. A waiter may ask me "What kind of Coke you want?" and I might reply Dr. Pepper. (This is Texas-- everything is called Coke.)

My brother cleverly ended this argument by saying, "When you open a can of coke, it says 'sssssss Pop!' It doesn't say 'sssssss Coke!"

He wins.