Place the quinoa in a fine-mesh strainer and rinse thoroughly with cool water to remove any bitterness.
Transfer the washed quinoa and measured water to a rice cooker. Start the cooker and cook for exactly 40 minutes. The cooker may signal it's done earlier, but do not lift the lid or stop the process until the full 40 minutes have passed.
While the quinoa cooks, prepare the dressing.
In a small non-metal bowl, combine the rice vinegar, honey or sorghum, sugar, and salt.
Whisk vigorously for about 2 minutes until the sugar and salt are mostly dissolved.
Set aside.
Once cooked, spoon the steamed quinoa onto a large, flat cutting board or a non-metal baking sheet.
Drizzle ⅓ cup / 80 ml (2.7 fl oz) of the dressing over the quinoa and toss gently with a wooden or plastic paddle to combine.
Add the remaining ⅓ cup / 80 ml (2.7 fl oz) of dressing and toss well to ensure all the grains are evenly coated.
Spread the quinoa into a thin, even layer and allow it to cool for 10 minutes.
Gently turn the quinoa over and let it cool for 5 more minutes.
Place the finished quinoa in a large non-metal bowl and cover with a damp, lint-free dishcloth until you're ready to make your sushi. Use within 4 hours for the best texture.
Do not skip rinsing the quinoa. This crucial step removes its natural coating, called saponin, which can have a bitter or soapy taste.