your dog empty (without a treat in it). hold the treat in your other hand hidden behind your back, for example, or just have it ready somewhere else, but out of sight for your dog. showing the treat would distract your dog’s attention from the hand.
your dog will likely try to find the treat again by bumping your hand again with the nose to sniff it or she will paw it again for the treat – depending on what you have trained before.
click, show her that your hand is empty and reward while letting her watch how you take the treat from somewhere else (your other hand for example).
repeat this 