Ah, but are you drinking the one you chose, or the one that you were going to choose because of things that occurred in the past? Maybe you had some crackers earlier that made you thirsty... and maybe you've got a subconscious preference for something colored (assuming you took the gatorade).

Maybe a better example is if you're standing in a totally empty, bland room with two doors (A and B). Neither door has any difference besides being on opposite sides of the room. You're going to choose the one you prefer based on past experiences.. maybe you subconsciously like the letter B more, or maybe you think turning to the right is better. These are tiny little things but they ultimately lead up to your decision.