a real CO2 cylinder with a CGA 320 valve (the 10lb size is plenty)
a CGA-320 CO2 regulator
some 1/4" ID reinforced PVC tubing
a carbonation cap + 1/4" barb ball lock disconnect (mentioned together because they’re often sold as a set), and
a plain old empty 2-liter soda bottle.
That’s everything you need to carbonate soda yourself without some proprietary bullshit device.
(I found the best price for the gas cylinder from a local company that resupplies restaurants etc. with soda dispensers, which is convenient because they can also refill it for you. The rest of the stuff can be found easily enough from Amazon or whatnot. I wouldn’t buy the cylinder from Amazon unless I wanted aluminum instead of steel, for no good reason.)
LPT: go get
That’s everything you need to carbonate soda yourself without some proprietary bullshit device.
(I found the best price for the gas cylinder from a local company that resupplies restaurants etc. with soda dispensers, which is convenient because they can also refill it for you. The rest of the stuff can be found easily enough from Amazon or whatnot. I wouldn’t buy the cylinder from Amazon unless I wanted aluminum instead of steel, for no good reason.)
Even better: get a soda keg, fill with water and charge with CO2. Seltzer on tap!
Works if you have space to put a 10lb CO2 cylinder
There’s also smaller 5# tanks
The paintball ones?
You have to make sure whatever you use is food grade. A paintball refill wouldn’t have to be and could contain weird oils you wouldn’t want to ingest.