In the First Bill and Ted’s, they’re breaking out all their historical friends from jail and Ted’s father confronts them. Ted says, “Garbage can. Remember a garbage can.”
Then BOOM! A garbage can falls from nowhere and they escape. So obviously they finish what they’re doing and then go back to that moment to drop a garbage can on the dad’s head.
Tenet is one big sequence like that. They’re on a mission and realize that something different needs to happen at a specific moment so they yell, “Garbage can” over and over again so they know when to come back to specific moments to help themselves out.
If only they had a Rufus to guide them.