Place the strawberries and juice in a small saucepan.
Bring them to a gentle boil
Continue simmering them until the strawberries soften
Place the liquid in a blender
Puree the ingredients to a smooth liquid. (Be careful, hot liquids in a blender can be explosive. Ask me how I know.)
Strain the blended liquid through a sieve. I stacked a six inch strainer on a canning funnel on a pint wide-mouth mason jar which worked great.
Refrigerate until cool
Add the syrup to seltzer water to the ratio that you prefer. I prefer lightly flavored, maybe two teaspoons to 8 ounces of seltzer. Other might prefer a 50/50 mix.
Recipe Notes
I thought I would need to add Stevia or something like that to the mix. However, the two fruits provide a nice combination of tart and sweet.