In a resealable bag combine the soy sauce, brown sugar, garlic, ginger, chile flakes and salt and pepper to taste. Add beef, seal the bag, and shake to coat the meat in the marinade.
Marinate the meat for at least 15 minutes or up to 2 hours.
In a small bowl, combine the cucumbers, rice vinegar, sugar and salt to taste. Cover and refrigerate for at least 15 minutes, or up to 4 hours.
Heat the vegetable oil in a large pan over high heat. Add the beef in a single layer and cook for 4-5 minutes until beef is cooked through and starting to brown.
While the beef is cooking, make the slaw. In a medium bowl, combine the green cabbage, purple cabbage, carrots, lime juice, olive oil and green onions. Toss until thoroughly mixed. Season to taste with salt and pepper.
To assemble place 8 flour tortillas on a flat surface. Fill each tortilla with approximately 1/4 cup slaw and evenly divide the beef over the tortillas. Top each taco with approximately 2 tablespoons of pickled cucumbers and serve.