1-First, start with the initial preparation by toasting the rye bread cubes. Preheat your oven to 120°C (250°F) and toast 1 cup of cubed sourdough rye bread for 1-2 hours until it’s dry and crisp, then let it cool this step enhances the flavor and readies it for fermentation.

2-Next, fill a sterilized 1-liter glass jar about two-thirds full with 3 to 4 cups of non-chlorinated water. Add 1/2 cup sugar and stir until it’s fully dissolved, creating a sweet base for the yeasts.

3-Now, for the first fermentation stage, add the toasted bread cubes to the jar and stir gently to mix everything. Cover the jar loosely or with a lid and place it in a warm, dark spot away from direct sunlight. Stir once daily and taste after 3 days; continue fermenting for 6-7 days or until you reach your preferred level of sourness. This stage is where the magic happens, as wild yeasts convert the sugars into that signature bubbly taste.

4-If you want to amp up the flavors, move to the second fermentation. Strain the mixture into a clean, sterilized 1-liter swing-top bottle using a funnel and sieve, then add optional flavorings like fresh mint, ginger, or cardamom pods, along with extra sugar or honey if desired. Cap the bottle and let it ferment for up to 24 hours in a warm, dark place, remembering to release gas periodically to avoid pressure buildup. Once done, refrigerate and enjoy within 3 days for the best taste and probiotic benefits.

5-For ongoing batches, after straining, you can immediately start a new one by repeating the first stage with the leftover starter it ferments faster and might need less sugar over time.