In a medium bowl, whisk together rice vinegar, sesame oil, sugar, soy sauce, salt, toasted sesame seeds, and red pepper flakes. Add cucumbers. Stir to coat.
2 tbsp rice vinegar, 1 tbsp sesame oil, 1 tbsp sugar,, 2 tsp soy sauce, ½ tsp salt, 1 tsp toasted sesame seeds, Crushed red pepper flakes