Here's a simple recipe I knocked together with some leftover syrup from some Strawberry Rhubarb pie filling I was making.
Step 1: Make pie filling. For a 10" pie, 1½ lb strawberries, diced, 1½ lb rhubarb, diced, 2 c sugar. Add to pot and heat to extract juices (~10-15 minutes). Use a strainer to separate the juice from the fruit. Return juice to pot and boil for an hour to reduce volume significantly. Stir as necessary to prevent scorching. When thick (if you have a candy thermometer, soft crack), coat fruit. Let drain for a minute, collecting the runoff. The coated fruit goes into a pie crust. The reducing step ensures that the pie will not be a runny mess. But, what to do with the excess syrup?
Step 2: Add seltzer. Yep, that's it. I make it by the glass, adding syrup to taste. You can add some lemon juice is you want it to have that refreshing kick. It's really up to you and your taste.