I like to make syrups, and then mix them to taste with sparkling water. Naturally carbonated ones are OK, but the yeast flavor can sometimes clash, and they have a much shorter shelf-life.
Here's the strawberry soda syrup I use -- is *amazing*, especially if you can get your hands on fresh, local strawberries that are at peak ripeness!
- 1.5 cups sliced strawberries
- 0.9 cups sugar
- 0.65 cups water
- 0.25 cup fresh-squeezed lemon juice
Simmer for 15 minutes, mashing strawberries as the pot comes to a simmer. Next, strain through a fine mesh strainer, and transfer to a container. Mix ~1 to 2 oz. with 8 oz. of sparkling water (or otherwise to taste). Sugar can be adjusted to taste.
If you want much lower sugar flavored sparkling waters, I highly recommend the Amorette Craft Puree series (which is also awesome for beer flavoring). A pump or two in a glass of sparkling water is really nice, and way cheaper than La Croix or even store-brand Faux Croix. The blood orange flavor is my favorite.