Congrats on making a positive change in your life and a really healthy switch. It's gotta be easier on your pocket too.
Don't let your sister's response bother you in the slightest, you're doing great!
You might be tempted to get a SodaStream but, aside from being produced by a company that operates out of the West Bank in Israel (so fuck them), I think that the economics of SodaStream don't really work out although YMMV depending on which country you're in.
If you foresee that your sparkling water consumption is going to stay high for a long time and you want to cut down on the costs and the waste, you can actually get a larger CO2 bottle, a regulator, and a few little bits and pieces so that you can carbonate your own water by reusing PET bottles. It does require a bit of space but if you've got some room to spare then it's a far better option than SodaStream.
(Or maybe hit up a person you know who is into homebrewing because they're probably interested in forced-carbonation and they might split the costs with you.)
I'm in the UK, we got a sodastream alternative but it's a pain getting non-sodastream co2 bottles for it. Initial cost means it took 3 years to break even compared to buying 2l's of carbonated water, but it's now about 1/3 of the price.
I think that's a part of theory on addiction, at lllleast like, AA's theory on addiction, that it's pretty common practice to replace one 'addiction' with another. My roommates drink sparkling water too though so it's pretty funny how many cans we end up with (though she has not had issues with alcohol
Get yourself a sparkling water dispenser and make your own at home! Less bottle waste and you can get refillable co2 containers for the device.
You can get sodastream alternatives, but it's worth doing the maths beforehand to work out whether it's cheaper - I've found it's much cheaper long term here in the UK, but it might not be where you are.
The way I operate is simple
If someone hands me a glass of water, I will drink it, water is good
If I am at home, I only drink out of cans
In fact, I am drinking a cherry vanilla seltzer right now as I type this
Specifics of container unrelated; brand name is entirety of message/reaction.
My dad did this exact thing. He ordered industrial sized cartons of Perrier
I used it to quit sugared sparkling beverages, should have used it for drugs lol. I drink almost exclusively fizzy water now, as in it replaces water for me, it's a problem