Plaidophile

So, lately I've been using my soda siphon again, especially at parties. A soda siphon is a little pressure vessel that takes a liter or so of water and a small CO₂ cartridge, and combines them to make fresh seltzer at home. They are best known as a classic prop comedy device. They are also much more convenient than bottled seltzer since you can keep about a hundred liters' worth of CO₂ cartridges in the space of about one 1-liter bottle, and they're also much more environmentally-friendly because you're just using municipal water, and the shipping of the cartridges takes very little fuel (I'd estimate at about a 300:1 ratio compared to the premade equivalent), and the discarded cartridges are 100% recyclable aluminum (unlike plastic drink bottles which degrade very quickly in the recycling process). Also, if you can get a good deal on cartridges, it ends up cheaper (or at least no more expensive) than the bottled stuff. The main downside is that the resulting seltzer isn't as bubbly as commercially-prrepared seltzer, but it still has most of the mouthfeel (especially when it's fresh and made with ice-cold water in an ice-cold siphon).

Since people have been interested in getting their own, there's not a whole lot you need. There are several soda siphons available (I have the iSi Soda Siphon Brushed Aluminum 2248), and then as far as cartridges go, you can often find them at restaurant suppliers or wholesalers (e.g. Cash and Carry). My most recent shipment came from Creamright, which specializes in these things (they also have N₂O cartridges for making whipped cream and/or getting high); I just use their generic CO₂ cartridges. They also have slightly better deals on siphons, too.

Anyway, the other part of the equation is that after you have a source of seltzer (and this works with bottled seltzer too), you can make your own soda with Torani syrup, which comes in a bunch of flavors, and is sweetened with sugar instead of HFCS (and they also have diet versions). I just buy that stuff at BevMo.

If you want soda that's brewed in a more traditional way, there are plenty of recipes out there for home-brewed ginger ale and root beer using a fermentation process, or you can cheat and get (or make) an appropriate syrup and mix it with seltzer (typically by making simple syrup and combining it with a flavor extract). That does generate a slightly different flavor, though, and a fermentation approach also produces a bit of alcohol (not enough to get drunk, but enough to cause problems if you have an alcohol-sensitive medical condition).