[aarongolliver]

soda stream is a lot cheaper than buying bottled sparkling water, and you can make a very good analog to your favorite mineral water / soda / energy drink for even cheaper if you buy the right additives online. They did do a good job of making their luxury version waste most of the CO2 tank because it's impossible to make a good airtight seal.

you can homebrew your own though, and use a much larger/cheaper CO2 source than what they sell at grocery stores, which I'll probably be doing soon.