This is really interesting. I have been making my own "instant cola" with several large dashes of angostura bitters and a can of seltzer in a pint glass. The liquid should be very pink/orange. and, if I want sweetness a drop of liquid sucralose sweetner is all I need, just sweet enough for me without aftertaste. This mix scratches my cola itch very well and can be made in about 20 seconds.

Fun fact: Angostura bitters has gentian root extract in it, which is also in the northeastern US's favorite regional soda specialty: Moxie! If you like that, you'll probably also like Moxie.

It's also a great way to taste bitters, generally, and a pretty decent substitute for a drink if you're trying to cut back.

Try walnut or cherry bitters sometimes for a similar but different enough to be interesting flavor.