Watery Stool Dog Vet Put My Dog On Metronidazole&canned Food,took Stool Sample Today And It Was Clean. Now She Had A Few Watery

Vet put my dog on metronidazole&canned food,took stool sample today and it was clean. now she had a few watery - watery stool dog

I took the stool sample today at the SPCA, where I work and have found nothing. That evening she went out and saw a couple of small jet in the driveway. It has been made of chairs, but then it happened. I believe it is nothing, I hope. Help!