Cody being a well known Hufflepuff the Rock gave him a piece of his soul letting Cody know The Final Boss will live forever to haunt him...
A Bottle of Lipgloss
It was a 4 page letter and Rock was making sure he got it on time….A love letter
I'm gonna guess he gave him Dusty's HOF ring, which Cody gave him for some reason previously until he somehow broke Rocks heart
Or he gave him the USB stick with all of Diddy's secret party footage.