What is the Mandarin equivalent of Cantonese's 一係 A 一係 B? In Cantonese, you can use 一係 to present two options. For instance, you can say:

"Either eat or go" => 一係食一係走

In Mandarin, someone said 或者 is similar but lacks the same emphasis and force.

In other words, Mandarin speakers wouldn't say 或者吃或者走 

So what's the Mandarin equivalent for 一係?
An equivalent expression is:
要麽 before each option

要麽吃，要麽走

Either eat or go.

要麽你去，要麽他去，我不能去。

Either you go or he goes; I can't.