The 34-year-old Joyce joins his third team this spring. He signed a minor league deal with the Giants on Wednesday after opening spring training with the Cleveland Indians.
Adam Duvall is hitting only .171 in his bid to make the Braves' roster as a backup outfielder.
Joyce hit .200 in a combined 14 games with Cleveland and San Francisco this spring. He hit .208 with seven homers in 83 games with Oakland in 2018.
The lefty-hitting Joyce batted .243 with 25 homers and 68 RBIs for the Athletics in 2017.