1 cup distilled white vinegar or rice wine vinegar
1 cup water
1/2 cup granulated sugar
1 tablespoon kosher salt
1/2 teaspoon whole black peppercorns
1/2 teaspoon red pepper flakes
2 firm avocados
Optional flavoring ingredients:
Place the vinegar, water, sugar, salt, peppercorns, red pepper flakes, and any additional flavoring ingredients in a medium saucepan. Bring to a boil, stirring occasionally to dissolve the sugar and salt. Remove the pan from the heat and let cool to room temperature.
Meanwhile, prepare the avocados. Peel and pit the avocados, then cut into 1/2-inch-wide slices or cubes. Place them in 2 (18-ounce or larger) canning jars. Pour the cooled brining liquid into the jars, completely covering the avocado pieces, and seal the jars. Refrigerate for at least 2 hours before serving.