QUOTE
"There has been no information on whether stardust will remain a form of gym reward under the new system. However, Niantic's gym FAQ states that feeding berries to defenders will yield stardust and XP, possibly replacing the old reward paradigm. In this preview video, feeding a berry to a demotivated defender yields 50 stardust."
https://pokemongo.gamepress.gg/news/gym-update-everything-you-need-know