In medium-sized bowl, combine the soy sauce, sugar and sesame chili oil.
Rinse the cucumber and pat dry. Trim the ends. Cut the cucumber in half lengthwise, then cut each half into pieces about 1/2" long. Add the cucumber pieces to the marinade, stirring gently, until the cucumbers are well coated with the marinade. Let stand for 5 to 10 minutes. Sprinkle the sesame seeds over the cucumber slices and serve with toothpicks.