Beat the eggs in a small bowl; season with vinegar, salt, and sesame oil. Beat lightly to combine.
Heat the vegetable oil in a well-seasoned wok or large non-stick skillet set over medium heat. Add the egg mixture and scramble until just set. Scoop out onto a plate and set aside.
Sprinkle the tomatoes with the sugar, then add to the hot wok along with the scallions (add a touch more oil if the pan is looking dry). Stir-fry until the tomatoes have softened; 2 to 3 minutes.
Return the eggs to the pan and toss well. Taste and add salt as needed. Serve hot.
Notes
To store Chinese Tomato Eggs, place leftovers in an airtight container and refrigerate for up to 3 days. I don't recommend freezing, as it can mess with the eggs' texture.For reheating, use a nonstick skillet over medium heat, stirring gently until warmed through, or microwave in short intervals, giving it a stir between each to make sure it heats evenly.