Seasonal quince gives this sweet soda from Anton Nocito of P&H Soda and Syrup its rosy color and tropical fragrance. Also Try:Cream Soda Syrup, Grapefruit Soda Syrup
Place quince, sugar, lemon juice, and salt in a medium saucepan along with 4 cups water. Cover and bring to a simmer over medium heat; let simmer for 2 hours.
Add more sugar, if desired, and let cool. Transfer to refrigerator and let chill overnight.
Strain and discard solids. Transfer syrup to an airtight container and keep refrigerated until ready to use, up to 2 weeks. To serve, fill a 16-ounce glass with ice cubes and add 1 1/2 ounces syrup; top with seltzer and stir to combine.