In a hurry and haven't prepared. the clerk usually reads your order to verify if that's what you ordered in the event that more than one car in the same Lane and up one after the other. So I never worry about it.
If I feel that I'm in a hurry or time is that important to me I will grab a Clif bar some fresh fruit to go along with my water bottle on the the door. I try to avoid feeling the sense of rushing especially when I'm surrounded by others who feel the same thing.