Combine the listed marinade ingredients in a small airtight container or a standard size mason jar until the sugar dissolves completely. You can microwave the liquid for 30 seconds to speed up this process.
Fill a small pot with enough water to fully submerge the eggs, then add the salt and vinegar. Bring to a boil over high heat, then reduce to medium-high heat for a steady simmer.
Gently lower the eggs into the water (use either room-temperature or fridge-cold eggs). Set a timer and boil for 6 minutes for runny yolks, 6 ½ minutes for jammy runny yolks, 8 minutes for jammy set yolks, or 10 minutes for fully hard-boiled yolks. If using fridge-cold eggs, briefly rinse under warm water for about 15 seconds to take the chill off before lowering them into the water, then add 1 extra minute to the cooking time for consistent doneness.
Prepare an ice water bath in a separate bowl while the eggs boil. Transfer the cooked eggs directly into the ice bath to instantly halt the cooking process. Leave them submerged until they are completely cold to the touch.
Gently tap the cooled eggs with the back of a spoon to crack the shells. Slide a spoon under the shell starting at the wider base of the egg where the natural air pocket sits to peel cleanly.
Submerge the peeled eggs into the soy marinade. Place a small piece of paper towel or plastic wrap directly on top of the floating eggs to keep them fully submerged. Cover with a lid and refrigerate for at least 6 hours or overnight, or up to 24 hours for maximum flavor depth.
Remove the eggs from the marinade and place them on a cutting board. Cut them in half lengthwise using a sharp knife and serve cold over hot ramen noodles or rice bowls.