Wash the cucumbers thoroughly.
Cut each cucumber in half lengthways, then cut each half in half again to create long quarters.
Place half of the dill, the garlic cloves and the peppercorns in the bottom of a large glass jar or bowl.
Pack the cucumber pieces tightly into the jar. Add the remaining dill on top.
Mix the sparkling water with the salt, stirring until the salt has completely dissolved.
Pour the salted sparkling water over the cucumbers, ensuring they are fully submerged. If necessary, weigh them down with a small clean plate.
Cover the jar loosely with a small plate, lid, or cling film with a few holes to allow gases to escape during fermentation.
Leave in a warm place out of direct sunlight. An ideal temperature is between 20°C and 25°C.
After 1–2 days, the brine should become cloudy and the cucumbers should taste pleasantly sour.
Transfer the cucumbers to a clean jar, pour the brine over them and seal tightly.
Store in the refrigerator and serve chilled.
They are best enjoyed within 1–2 weeks and will continue to develop flavour as they mature.