Oh No, She Didn't!
Me: "She did what?" Her: "She sprayed my dog in the face with bitter apple spray"
Me: "What was she trying to demonstrate to the dog?" Her: "Leave it" Me: "I see"
Well. There's plenty of crappy training out there. I too started from humble beginnings. Firstly, I'd like to congratulate my client for walking out the door when this happened. Above all we are the guardians of our dog's feelings and emotions. So I guess I can understand that 'in nature' it would make sense that if a dog were to get sprayed by a skunk it might avoid the next one. After all, skunks can blind you with that. But here's the deal about adding something unpleasant (aversive) in order to decrease a behavior: the learner dictates how they feel about the whole situation. So it could go wrong in a handful of ways. That's the thing about the fallout of punishment, The learner gets to have the feelings about it. Usually what I see is that the dog has learned that their human is inconsistent and untrustworthy. Then I have to go about teaching someone how to fix that. I'm sure you have similar feelings about that friend you thought was a friend but is mostly a flake.
Your relationship with your dog is a lot like a fart.
If you have to force it, it's probably shit.
What if the dog doesn't learn that it's stealing from this surface that earns the spritz? What if the dog learns that it's you, you make the bad things happen? If the dog has already won a few slices of pizza and sandwiches it's going to be an uphill battle. If there's already been a few big wins we will need establish a more powerful reinforcement history for leaving things on the counter top.
If it has never happened in the first place we don't have any undoing to do. Easy peasy. We have to teach the dog that he should probably back away from the food in order to earn some other food. That's something that takes skill and a little science to achieve. It's a process that preserves the relationship and enhances communication between the two parties. Training with your dog is mostly just clearing up communication trouble, and enhancing happy feelings. Mostly anyway.