Rinse out the pot, then put it back on the stove over low heat. Pour the strawberry juice back into the pot. Add sugar, vanilla, and a dash of salt.
Set aside (or refrigerate) covered, and let cool. You now have a strawberry syrup. The ratio of syrup to carbonated water is 1:3. For a single small serving, I use 1/3 cup syrup and 1 cup carbonated water.
First pour the carbonated water into your glass/cup/jar. Then slowly add the syrup. There will be fizzing and foaming, and that’s a good thing :) Add some ice, and you’re good to go!
Strawberries are quartered, so they fill the pot better during cooking. I like to buy the small 10 fl. oz. bottles of carbonated water, because they are good for a single serving and are sold in 6-packs where I buy them.
If you want a cold soda, I suggest refrigerating the carbonated water first. Otherwise, you can always add ice later. Anyway, on with the show!
Let's begin! Cook the strawberries in simmering plain water using a small sauce pot. The strawberries will turn into mush, and the water will turn red with a fresh and tart strawberry flavor.
I use a potato masher to mash the strawberries until all of the big chunks are smooshed. This is also the start of a good jam, but we’re sticking to soda today.
Strain the liquid into a bowl using a fine-mesh strainer. I also use a wood spoon to press any liquid out of the strawberry mush and into the bowl. The leftover strawberry mush can be stored and used for other purposes: strawberry filling, strawberry spread, and whatever else you might think of :)
Refrigerate syrup until cool.
Combine strawberry syrup with cold carbonated water.