In a small non-reactive saucepan (stainless steel or similar), combine the water, vinegar, salt and sugar. Bring to a simmer over medium heat and whisk until the sugar and salt have dissolved. Remove from the heat and set aside to cool.

Divide the mustard seeds and dill heads (if using) between the jars and pack each jar tightly with the cucumbers, dill sprigs and garlic.

Pour the cooled brine (it can still be slightly warm) into each jar over the cucumbers to cover. Cover the jars with the lids and place in the refrigerator for 2-3 days before enjoying or for up to 1 month refrigerated.