PIckled Eggs

• 12 hard-boiled eggs
  , cooked and peeled
3 cups white vinegar (or cider vinegar)
1 cup water
1/3 cup sugar (optional, for balance)
2 tsp kosher salt
2 cloves garlic, smashed
2 tsp pickling spice
1/2 onion, sliced (optional)
1 tsp red pepper flakes (optional, for heat)