Cut 3 lemons and 2 limes in half and juice them using a citrus juicer or hand juicer to yield about 1/2 cup lemon juice and 1/4 cup lime juice.

Pour the citrus juice through a fine-mesh strainer into a clean container, removing pulp and seeds for a smooth base.

In a small pot, combine 1/4 cup sugar and 1/4 cup water, bring to a boil until sugar dissolves, then remove from heat and let the simple syrup cool completely.

In a large pitcher, whisk together the strained lemon juice, lime juice, cooled simple syrup, and 2 cups of chilled filtered water until fully combined.

Add 1/8 teaspoon of sea salt to the mixture and whisk until fully dissolved to enhance the citrus flavors.

Taste the base mixture and adjust by adding more lemon juice for tartness, simple syrup for sweetness, or lime juice for complexity as needed.

Refrigerate the base mixture for at least 30 minutes or until very cold to ensure better carbonation and a refreshing temperature.

Just before serving, add carbonation by charging the chilled base in a carbonation bottle or siphon according to the manufacturer's instructions, or slowly stir in 1 cup of chilled carbonated water.

Pour the carbonated soda into ice-filled glasses immediately and serve right away to enjoy peak fizz and flavor.