Use common sense.
A little common sense always goes a long way. Is it a hot day? Did they just have a long walk or excessive play? If your dog is drinking water in those situations, you may already have your answer.
However, it’s important to not downplay excessive thirst either. Super thirsty dogs may be trying to tell us something: they aren’t feeling well!
Ask yourself questions like, "Is she peeing more often?" "Is she behaving differently?" If you're not sure, as always, call your veterinarian and set up an appointment. Safe is better than sorry!
Run a diabetes check.
Here's a good video outlining dog diabetes and what to watch out for (thirst can be a symptom).