Prior to elected office, Sonny was a college instructor, journalist, youth mentor, and artist. He is an alumnus University of Hawaii at Manoa William S. Richardson School of Law and the University of California at Los Angeles.  As a lawyer, he has been a staff attorney at the Domestic Violence Action Center and a court-appointed attorney with the District Court. He has taught in the American Studies and Ethnic Studies Departments at the University of Hawaii at Manoa, edited and written for local magazines, managed a youth program for young men and boys at the healthcare center Kokua Kalihi Valley

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As an attorney, Ganaden defended the rights of Native Hawaiian elders who were arrested for protesting the construction of the controversial Thirty Meter Telescope. Ganaden was also the lead writer on the Native Hawaiian Justice Task Force Report, which concluded that Native Hawaiians were disproportionately and unfairly overrepresented in Hawaiian prisons. Ganaden has criticized the existence of private prisons and worked towards justice reform,

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Ganaden was previously an instructor at the University of Hawai'i at Mānoa, teaching in the departments of American studies and ethnic studies. Ganaden contributed an essay to Detours: A Decolonial Guide to Hawai’i, where he wrote about King Kamehameha I's impact on modern Hawaiian law.

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Ganaden after managed a youth program for young men and boys through Kokua Kalihi Valley called VIBE - Kalihi Valley Instructional Bike Exchange program.  There Ganaden was a mentor to these young men guiding them to strengthen their connections to Aina, and others, past and present, and better through engaging the youths in sustainable waste management and land stewardship through bicycle refurbishment.

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