To make dressing: In food processor, pulse orange soda, lime juice, olive oil, cilantro, avocado and garlic until consistency is smooth.
To make quinoa salad: Cook quinoa according to package directions and let cool.
Once quinoa is cool, add to bowl with orange pieces, if desired; grapefruit pieces, if desired; lime juice; avocado, if desired; feta cheese, if desired; and diced onion, if desired. Top with orange cilantro salad dressing.