To ask someone to do something as soon as possible, you can add 尽快 (jǐnkuài, as soon as possible) before the task you want them to do.
请尽快回复。
Qǐng jǐnkuài huífù.
Please reply as soon as possible.
请尽快离开！
Qǐng jǐnkuài líkāi!
Please leave as soon as possible!
请尽快把报告写完。
Qǐng jǐnkuài bǎ bàogào xiě wán.
Please finish writing the report as soon as possible.