Pour in the wine, sparkling orange soda, Campari, and triple sec into a large pitcher. Add the sliced oranges and lemons and give the mixture a stir. Refrigerate for at least a few hours, until well chilled.
Serve in big wine glasses (or the glasses of your choice) over lots of ice, making sure to scoop some slices of citrus into each glass.
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Notes
I think the best white wines for sangria are Pinot Grigio, Sauvignon Blanc, a dry Reisling, or Vinho Verde. Steer clear of those oaky, buttery California whites, like Chardonnays, which have a lot of sweetness to them and can be cloying in combination with the fruit and added sugar.
Consider making some orange juice ice cubes, which look cool floating around in the drink and will add more tart-sweet flavor to the sangria as they melt.
If you want a less alcoholic version of this sangria, you can top off the glasses (or the pitcher) of sangria with some sparking water. This will add more fizziness (the orange soda also adds a nice bit of effervescence) and also tone down the alcohol level. Offering a bottle of chilled sparkling water with sangria allows people to decide how strong they want their drink to be.
For extra visual appeal, mix up all kinds of sliced oranges for garnishing the glasses: look for blood oranges, Cara Cara, Satsumas, and Valencias. You could also slice up some lemons or lime for that extra wow factor; Meyer lemons are lovely if available. You can also freeze the orange slice to help keep the drink cold.
Try adding some frozen strawberries to help keep the drink cold and add pops of red.