If your dog readily drinks fresh water from a different bowl, start by making that safe option available. A bowl can be noisy, slippery, too tall or placed somewhere the dog does not feel comfortable. Do not withhold the working bowl to force a preference for the old one. Make sure other animals cannot block access.
Track how much your dog drinks across the day and whether they urinate normally. A change in total drinking, weakness, vomiting, dry gums or trouble keeping water down needs veterinary advice. Seek urgent help if your dog seems dehydrated or ill. The article on a sudden increase in drinking covers the opposite pattern and why the amount matters more than bowl loyalty.
Wash both bowls and try the one your dog accepts in a quiet, stable spot. Notice whether a collar tag taps the edge, the bowl moves across the floor, or another dog watches them drink. Change one part of the setup at a time while preserving access to water. Dogs Trust notes that bowl type, placement, sound and anxiety can affect drinking, but a vet should assess a real intake change.
Today, offer the working bowl and note actual drinking and urination. A dog who has a usable water source does not need to win a standoff with a dish.
Sources: Dogs Trust on bowls and changes in water intake, VCA on urgent illness signs.