Place the eggs in a saucepan and cover with cold water.
Bring to a boil, then cover, remove from heat, and let stand for 12 minutes.
Transfer the eggs to an ice bath until completely cool.
Peel the eggs carefully.
Combine the vinegar, water, sugar, salt, pickling spice, peppercorns, bay leaves, garlic, and onion in a saucepan.
Bring the brine to a gentle boil and simmer for 5 minutes.
Remove the brine from the heat and allow it to cool slightly.
Place the peeled eggs into a clean glass jar.
Pour the warm brine over the eggs until fully submerged.
Seal the jar and refrigerate.
Allow the eggs to pickle for at least 3 days before serving.
For the best flavor, let them pickle for 5–7 days.