Clean/Format a USB stick that windows cannot handle anymore

OK, you need a Linux based system to do so.

Without the Memory stick being plugged into the Linux system,use the following command:

lsblk

Now plug in the usb Memory stick and use that command (again):

lsblk

The “new” device name should be easy to spot

Now, flaten the content of the Memory stick by using

mkfs.ext2 /dev/sdX

where sdX is the device name you found with lsblk.