Spam musubi is usually served at room temperature, but it can be served either hot or cold. If you prefer your Spam musubi warm, you can heat it up in the microwave. When reheating Spam musubi, make sure not to overheat it as this will cause the rice to become dry and hard. You can also opt to serve your Spam musubi chilled by storing it in the refrigerator for a few hours before serving. To ensure that your Spam musubi stays moist and flavorful regardless of whether you serve it hot or cold, be sure to wrap each piece securely with plastic wrap or aluminum foil. Enjoy!