Grate the fresh ginger until you have about a cup.

In a large mixing bowl, combine the grated ginger, sugar, and lemon juice.

Pour in the filtered water and stir well until the sugar dissolves completely.

Sprinkle the champagne yeast over the mixture and give it a gentle stir.

Cover the bowl with a clean kitchen towel and let it sit at room temperature for 24 hours.

After 24 hours, strain the mixture using a fine mesh strainer or cheesecloth into another clean bowl.

Using a funnel, carefully pour the strained liquid into your glass or plastic bottles, leaving some space at the top.

Seal the bottles tightly and let them sit at room temperature for 3-7 days.

Check them daily for pressure, and refrigerate once they are fizzy enough for your liking.