Any Tips To Stop Reverse Sneezing Episodes In A Dog?

My 4 year old yellow lab has a serious reverse sneezing problem. He has been checked thoroughly by our vet, there are no underlying conditions causing them. She assures me that they are harmless. I am sure they aren’t harming him, but they are harming our sleep…and he seems very uncomfortable during them. We’ve tried changing him over to all-natural food. He does it year-round.
I have tried all the tips that I have read, to no avail. I have tried pinching his nostrils shut, rubbing his throat, tugging gently on his tongue, and giving him something to eat.
Anyone have any tips that have worked for them? I am pretty desperate to find a ‘cure’ for this…