In a small bowl, whisk vinegar and oil. Season with salt. Add chili and onion and toss. Let stand 10 minutes.
Arrange pineapple on a platter. Top with cashews, sprouted quinoa, and mint. Drizzle with chili-onion mixture.
To sprout your own quinoa, place 1/4 cup quinoa in a mason jar and cover top with cheesecloth. Secure with metal ring or rubber bands. Fill jar with water and let quinoa soak overnight. Drain. Rinse quinoa with water and drain twice a day for up to 2 days, until roots are about 1/2-inch long. (Quinoa should not dry out completely.) Once sprouted, rinse thoroughly and use immediately or transfer to an airtight container and refrigerate for up to 2 days. Makes 1/2 cup sprouted quinoa.