Enjoy your bill
Free gifts are a relatively easy way for businesses to endear themselves to customers while getting a tax break. The business looks super-generous and the customer feels appreciated, and as if they’re getting something extra than what they paid for. If you get it right, you’ll have a loyal customer who’ll end up spending more on the return than the gift cost you in the first place.
It feels like this business owner has missed the point of a gift, and also doesn’t really understand the word “enjoy.” The label and the initial wording definitely imply that you are being given a complimentary bottle of water, but the small print is key in this situation. I hope that they read it before they’d opened 5 of the drinks.