I make my own fizzy water at home. I don’t drink soda and I started drinking carbonated water in ernest when they got the fizzy machines at Google (Vivreau and my favorite Natura). I ended up bringing in my own bottles to fill up to drink at home rather than spend a fortune on Crystal Geyser water. I let kitchen staff know what I was doing, honest.
Then I left Google and the new place had a sodastream which ended up being too much of a pain and never tasted very fizzy to me. Eventually I got my own setup at home. Here’s what I use.
I have a large 20lb CO2 tank, you can surely get by with a little 5lb one. don’t bother buying a nice new one from Amazon, because as soon as you take it in to refill, they’ll just exchange it for some old shitty one. I exchange mine at the local welding supply store, it costs about $30.
I turn off my co2 at the tank when I’m not using it. that’s why I need to adjust the regulator since it sometimes blows the pressure relief if you turn it on after a while. I make my fizzy water in batches of 4 liters. Two, 2 liter bottles. Fill them to about 2 inches from the top. put everything together, squeeze out the air while you screw on the blue fizzer lid and then slowly fill with gas and then shake. I keep 4 liters of still water in the fridge. Cold water gets more fizzy. Right after I’ve made it, I decant it into 8 grolsh beer bottles. These are cheap and come with free beer. Then fill up the soda bottles and put them in the fridge ready for the next batch. Turn off all the gas.
I end up making around 40 liters of fizzy water a month and that 20lb/$30 co2 tank lasted almost 2 years.
If you want always on fizzy water at home, there are a few systems out there, none of them looked very good to me and I love the ice cold water out of Grolsh bottles I’m currently making. You could get a soda keg and hook that up to make your water in 5 gallon batches. I actually have one I’m looking after for someone but have never bothered to set it up.