Wash the carrots, cucumbers, and radishes under cold water. Slice the carrots and cucumbers into thin matchsticks and cut the radishes into rounds. Set aside in a bowl.

In a medium saucepan, combine 1 cup of water and 1 cup of vinegar over medium heat. Stir in chopped green onions, sea salt, oregano, and sugar. Bring to a gentle boil and let dissolve for 3-5 minutes.

Layer the prepared vegetables in a clean mason jar, compacting slightly. Once the brine has cooled, pour it over the vegetables, ensuring they are fully submerged.

Let the jar cool at room temperature for about 15-20 minutes, then seal it with a lid.

Refrigerate for at least 1 hour before enjoying. The flavors will deepen over time.