A dog can be given probiotics daily if they need them.
However usually just giving the dog dog probiotics once or twice per week is good enough to keep them healthy unless the vet says they need probiotics daily.
You're not gonna harm the dog though if you do give them daily probiotics if you want too give it to them that often.
When you give the dog probiotics daily or once or twice per week it will help with things such as inflammatory bowel disease, food allergies etc.
When you first give your dog probiotics it's recommended to give it to them daily and then after a month you can start giving the probiotics to them once every other day.