As with all sources, how you cite a State of the Union address depends on how you accessed it. A video of Gerald Ford’s 1976 address uploaded to YouTube would be cited as follows:

“1976 State of the Union Address (January 19 1976).” YouTube, uploaded by theCarbonFreeze, 21 Nov. 2017, www.youtube.com/watch?v=jWxtu8xdZU0. Accessed 7 July 2021. 

A transcript of Jimmy Carter’s 1980 State of the Union address republished on a website would be cited this way: 

Carter, Jimmy. “State of the Union Address 1980.” 23 Jan. 1980. The Jimmy Carter Presidential Library and Museum, University System of Georgia / The Carter Center, 24 Sept. 2020, www.jimmycarterlibrary.gov/assets/documents/speeches/su80jec.phtml. Transcript.

If you listened to an audio recording of Franklin D. Roosevelt’s 1941 address online, the works-cited-list entry might look something like this:

Roosevelt, Franklin D. “January 6, 1941: State of the Union (Four Freedoms).” Miller Center, Rector and Visitors of the University of Virginia, 2021, millercenter.org/the-presidency/presidential-speeches/january-6-1941-state-union-four-freedoms. MP3 file. 

If the medium of publication would otherwise be ambiguous, you might add it in the final supplemental element, as shown in the last two examples, where “Transcript” and “MP3 file” have been added for clarity.