Heat a saute pan over medium heat. Add the spinach, oil, sugar and soy sauce. Cook the spinach, stirring, until the leaves are just wilted, about 3 minutes. Spread the spinach out flat on a plate to cool quickly in the refrigerator for 10 minutes. (This will keep it a vivid green.)
When the spinach is cool, taste and correct seasoning. Pile in a bowl and sprinkle with toasted sesame seeds.