No lock-in (adversarial interop is fine)
I didn’t realise Sodastream had a lock-in mechanism, which means buyers not only support Israel w/the purchase but they are in fact forced to continue supporting Israel. The DiY page you linked says this:
It uses no electricity (no microchips, like some Soda Stream systems).
Oof.. so IIUC, Sodastream needs electricity for the purpose of powering a vendor lock-in mechanism. yikes.
In my area, the streets are littered with N₂O tanks because making whipped cream is /very/ popular (particularly around university campuses). I wonder if those tanks can be repurposed for fizzy drinks. I heard they are spec’d to handle around 100 bar, which is far beyond what would be needed.