Elvis Presley only made one product commercial in his career. What was the product and advertised name?

Doughnuts (Southern Maid) in 1954.

NOTE: Elvis did the only commercial of his life for any product on November 6, 1954, for Southern Maid Donuts. He sang their jingle. "You can get 'em piping hot after four PM, you can get 'em piping hot. Southern Maid Donuts hit the spot, you can get 'em piping hot after four PM." Nothing is known of Elvis's impact on Southern Maid Donut sales.

http://www.southernmaiddonuts.com/

Elvis Presley loved jelly donuts, and his favorite store was
Southern Maid on Hearn Avenue in Shreveport, Louisiana. Elvis made only one
commercial in his {life;} that was a radio commercial for Southern Maid Donuts
that aired on the Louisiana Hayride radio program that ran in 1954.

http://www.tvacres.com/advertising_endorsements_NS.htm