The numbers I heard is that reusing a bottle is less energy intensive than melting it down. It’s sanitary if you sterilize it properly by heating to >100°C, which is still much less energy than heating it to 1723°C to melt. As for water, I try to think on a 100 year time scale, where water is a renewable resource, but plastic is not.
It’s true that the energy savings will be wasted if you end up trucking the pallet of glass soda bottles all the way across America! But you shouldn’t be trucking bottles that far anyway - you should be sending rail tanker cars full of syrup to a bottling plant in each state and use local water to mix it.