In a pot, combine the white vinegar, water, sugar, pickling spice, garlic, and red pepper flakes. Bring to a boil over medium-high heat, stirring to dissolve the sugar.
Add the sausages to a clean, heatproof jar.
Pour the hot vinegar mixture over the sausages in the jar, ensuring they are completely submerged.
Seal the jar with a lid and let it cool to room temperature. Once cooled, transfer to the refrigerator.
Allow the sausages to pickle for at least 3 days before serving, shaking the jar occasionally to distribute flavors.