In a medium saucepan, combine the sliced ginger and water. Bring to a boil.

Once boiling, stir in the granulated sugar until it dissolves completely.

Reduce heat and let the mixture simmer for about 5 minutes.

Remove the saucepan from heat and let the syrup cool to room temperature.

Once cooled, whisk in the active dry yeast and fresh lemon juice.

Pour the syrup into a large pitcher and cover it with a clean cloth. Let it sit at room temperature for 24 hours to ferment.

After fermentation, strain the mixture through a fine-mesh strainer into a clean container.

To serve, mix the ginger syrup with sparkling water to taste.