1. Make the quick cucumber pickle: Add the thinly sliced cucumber to a medium zip-top bag or container with a lid. Add the apple cider vinegar, sugar, and salt. Seal and shake until the sugar dissolves, then transfer to the refrigerator to pickle while you prepare the sauce and noodles.
2. Cook the somen noodles according to package instructions, then drain. Transfer the noodles to a large bowl of ice water and stir for 30 seconds, then drain again. Place the noodles in your serving bowl and refrigerate while you make the sauce.
3. Make the ketchup sauce: add the sesame oil, soy sauce, apple cider vinegar, ¼ cup of pickling liquid from the pickled cucumbers, sugar, gochugaru, sesame seeds, ketchup, gochujang, and garlic to a jar or container with a lid. Seal and shake until the sugar dissolves and everything is well mixed.
4. Remove the noodles and pickled cucumbers from the refrigerator. Pour the sauce over the noodles and toss to coat. Top with the pickled cucumbers and jammy eggs. Finally, garnish with additional ice cubes and a sprinkle of furikake, if desired.
5. Enjoy!
