You might drop a pinch of baking soda on the liquid--if it is vinegar or battery acid, it will fizz, water will not.  If it fizzes, then wafting your hand over the liquid to get a smell of it could help you tell if it has the smell of vinegar, battery acid doesn't smell like vinegar.

A clear puddle of liquid underneath your car in the driveway would more than likely be from the air conditioner which means it is just water. You could tell right away if it was battery acid or vinegar due to the smell it would emit. Also, battery acid would most likely damage the driveway. You would want to be careful if you are going to get close enough to smell it just in case it is battery acid. Battery acid contains sulphuric acid which can be very damaging to the skin.