I'd add that the soda that comes out of those bulk dispensers is so cheap, it is hardly worth policing.
While not necessarily inaccurate, this comment reflects misconception on two levels.
First: When you buy a soda at the fast food restaurant or cafeteria, you're paying for the
value of having that drink. Value is all about perception. There are myriad case studies where sellers withdrew an inexpensive offering from the market, did a little redressing, and the reintroduced effectively the same product at a substantially higher price-point, turning a poor performing into a profit superstar. Think about the impact on perception - the impact on value - from a customer thinking that the product they just purchased could have simply been taken, or worse a customer witnessing that thing they just paid for being simply taken by someone else.
Second: The cost of a drink at a fast food restaurant or cafeteria necessarily includes the cost of the water, the cost of the syrup, the cost of the cup, the cost of the lid, and the cost of the straw, but also includes part of the cost of the machine, the cost of the staff to maintain the equipment and keep the filling station clean and operable, but most importantly, the cost of customer acquisition. A "thief" isn't a customer, I know, but a casual attitude toward theft may adversely impact the value perceived by actual customers, and may even raise the cost of customer acquisition, if the theft adversely impacts the customers' experience. And remember, something may seem small to you, but multiply it by thousands or tens of thousands - or millions - and small becomes significant.
And secondly, according to an article that I read recently, the dispensers are really germy due to the refilled cups touching the dispenser nozzles. So, you might want to buy a bottled drink.
Good point and good advice!