With a veggie peeler, take off the guava peel. Add to a food processor and pulse until smooth.
If you'd like to discard the guava seeds, press the guava mixture thru a fine mesh strainer. Add the guava back to the food processor.
Peel the papaya and discard the seeds. Add about 1/2 cup of the papaya to the food processor. Reserve the remaining papaya for another recipe.
Add the juice of 2 limes and, if you desire, sugar to the food processor. Pulse until smooth. Scoop into an airtight containter. Refrigerate at least 2 hours.
Before serving, add the sparking water or wine to the container. Stir to combine and serve.
