Dog treat to stop drooling?

We have a puppy that drools constantly, due to his breed. Someone told me about a biscuit that a friend of theirs used to buy for their St. Bernard to cut down on the slobber, but they knew these people several years ago, so the dog owners aren’t around to be questioned, and google isn’t bringing anything up. Does anyone know what the treat could have been, or of any other safe way reduce the slobber?

Alum?

Maybe. A search didn’t bring anything up though, besides it being poisonous in larger quantities, so I won’t be mixing anything up on my own. Thanks for replying.