They say it upsets the stomach, causes digestion discomfort. Quite the reverse, it soothes the stomach, and eases discomfort.. As far as I know no one in my family ( all soda drinkers), has had anything to do with indigestion or stomach problems.
Soda water is also 'accused' of weakening the bones; no real evidence in this respect either.
I'm used to drinking it from an early age. In my childhood days, soda water was produced in a small factory where special glass bottles got filled with water and Co2, and then sold to customers. To buy a new bottle (named syphon), one had to return the empty one.
syphon*
At first, the device for soda making at home was the sypholux - a metalic, opaque, silver colored item (covering a glass inner bottle) which came with a plastic cartridge holder. To operate it one had to buy a package of replaceable Co2. cartridges. The more cartridges used, the stronger the soda. Usually three (3) cartridges were the optimal number for a fairly strong soda.
(The grey-red sypholux was a popular wedding gift in those days, and subject to a lot of jokes , as the newly wed couples used to get more than two or three of them ).
bottle, head, cartridge, cartridge holder*
inserted cartridge holder *
The sypholux and cartridges got replaced after a while by the Soda Stream company's device - a reusable bottle and a replaceable carbonating cylinder.
I wasn't happy with that method - too awkward and expensive for me.
soda stream kit*
Nowadays, I usually buy ready made soda water bottles /cans at the supermarket or kiosks. The bottles come in two sizes: family bottles and smaller personal bottles. It's important to read the label on the bottle before buying, as there are sometimes additions like sodium ,for example, supposed to give the soda better taste.
* web pictures