We all know the easy way to empty the garbage out of the recycle bin on Windows. Right-click on the Recycle Bin on the desktop and simply choose Empty.

Can it be done through a command-line so it can be part of something like a scheduled job or login script?
Sure thing apparently. Run the following in an elevated command prompt window.
rd /s %systemdrive%$recycle.bin

Note that if you have more than drives in your system, you need to clean them up individually.
Now, if you are familiar with PowerShell, Clear-RecycleBin is your friend.
Clear-RecycleBin
The cmdlet alone will clear all the local computer’s recycle bins. And you need to run it in an elevated PowerShell window.

With the -force switch, you can suppress the confirmation if you want to.
Clear-RecycleBin -Force
And if you only want to clean up the recycle bin on a certain drive, use the -DriveLetter switch
Clear-RecycleBin -DriveLetter D
Here is a bonus tip: how to open the recycle bin from a command line.
Start Shell:RecycleBin