Disposable or in theory 'recycleable' plastic bottles are probably not the best option but yeah refillable 5 gallon drinking water bottles aren't a bad idea. We use them in order to get reverse osmosis filtered water from the grocery store because the water generally tastes better than tap. Even separate carbon based water filters are useful to clean tap water to a higher standard. Getting people better tasting water would probably also help people avoid drinking sugar-based soft drinks or single-user disposable water bottles.