The QR codes could also be used to gather data about your customers - what's their favorite drink? How much do they drink per visit? What size drink do they prefer?
I think you could get this data by tracking (1) How many people came in, potentially via number of meals sold (2) How many times you have to re-order each type of drink. It wouldn't be real time but the data presumably already exists. Plus nowadays I see those fancy electronic dispensers with touch screens and would be very surprised if they didn't have built in metrics.
