Wash the feijoas thoroughly under cold water. Trim off the ends and slice each feijoa into quarters or smaller pieces. You can leave the skin on, as it adds flavor.
Place the sliced feijoas into a clean glass jar with a tight-fitting lid.
Pour the vodka over the feijoas in the jar. Ensure that the feijoas are fully submerged in the vodka. Leave a little space at the top of the jar to allow for shaking.
Seal the jar tightly and store it in a cool, dark place (like a cupboard or pantry) for at least one week. Shake the jar gently every day to help release the flavors into the vodka.
After the desired infusion time, strain the vodka to remove the feijoa pieces using a fine mesh sieve, cheesecloth, or coffee filter.
Transfer the infused feijoa vodka back into a clean bottle or storage container and enjoy chilled over ice or use it in cocktails.