Ashley, while it could be funny, it could also cause a lot of issues. My male dog likes to sniff, he rarely marks on anything that isn't a plant, unless tons of dogs have, such as the wall outside of Petsmart...it is actually stained with urine. But, he sniffs everything...people...cars...birds...everything.
He is also terrified, horrified, has panic attacks when it comes to water. It takes me sitting in the bathtub and holding him while my fiancée washes him to even get him to be calm enough to bathe...and even then, he is crying and shaking the entire time. We have had him since he was 7 weeks old...he has never had a bad water experience, never been near drowning, never been alone in the water. We have bathed him every other weekend for over 2 years...it gets no better. He is just terrified.
So, if he was sniffing something and he got sprayed in the face with water...I would lose it on the vendor. Because it would cause severe emotional distress to my dog, which can cause physical distress. He would likely then damage stuff near him as he tried to get away from the water and away from me. It would probably take me about 5 minutes to even calm him enough to be able to get him out of the booth.
As a dog owner, I believe dog owners should watch their dogs, or be financially responsible for anything their dog ruins. If my dog marked a tablecloth at a market, I am the type of person that would pay for it. But, I am also the type of person who called the cops on a lady who kept spraying my dog with water because he kept getting too close to where she was sitting (mind you, we were in an off-leash dog park).