Cook pasta according to package directions. Drain. Rinse the cooked pasta with cold water then drain again.
Place cooked pasta in a large bowl. Pour teriyaki dressing over the pasta. Gently toss to coat pasta in dressing. Cover with lid and place in fridge for at least 2 hours or up to 24 hours.
When ready to serve add the mandarin oranges, craisins, green onions, sesame seeds (if using) and baby spinach. Toss gently to combine everything then serve immediately. Enjoy!