We would never tell you to go out and get a Sodastream just to make cocktails like this, but if you have one, here's something else you can use it for beyond just making soft drinks or soda water. The folks at VinePair have a few great cocktail recipes that actually work well in the Sodastream and turn out drinks you'll want to share.
Cocktail picture from Shutterstock
Among some of the great cocktails VinePair suggests here are a tasty-looking bourbon fizzy lemonade (water, lemon juice, stevia or another sweetener, and two shots of bourbon), a more complicated -- but great sounding -- drink called "Hemingway's Stars," an effervescent take on a classic Hemingway, and a grapefruit margarita fizz that's perfect for a hot day. They're all easily made, require no solid ingredients (even the stevia is supposed to be liquid stevia), and the link below shows you exactly how to make them, that is, when the process isn't "combine all the ingredients into the Sodastream and push the button."
Now, Sodastream owners may know that the instruction manual says not to use anything but water in these things -- and that's usually good advice, since the unit can only generate so much pressure to carbonate water. Denser liquids and solutions, suspensions and other thicker liquids might take more pressure, and well, if the Sodastream can't produce it, that CO2 has to go somewhere, doesn't it?
We like the approach VinePair takes here (they only fill the bottles up part way, and use recipes that are heavy on water and spirits that have decent water content, for example), and we're always a fan of voiding warranties, but still, be cautious and don't get overzealous if you want to try these at home.