It would be better if you would provide your precise objective as it relates to your query...
1. Is the "source" drive a USB flash drive and does it contain a (presumably) bootable OS?
2. If that is so, is your objective to clone the contents of that USB flash drive to an internally-connected HDD/SSD so that the latter would be a bootable drive?
3. Or are you referring to cloning the contents of one USB flash drive to another USB flash drive?
4. When you refer to a "bootable USB stick/drive" you're not referring to such a device that merely contains the OS setup files, e.g., the Windows Media Tool, are you? Or is that the type of device you're talking about?
5. Is this a "one-shot" deal or would it involve multiple uses involving disk-cloning operations?
Provide a clear picture of just what your objective(s) is (are).