Persistent flash drives made using the leading boot drive creators such as mkusb, Unetbootin, Rufus, YUMI, etc do not come with a Guest user, as does a normal desktop install or Full install to pendrive.
It is possible to log into a flash drive using
Try Ubuntu, which will also permit a temporary session, however there is too much privilege with a
try Ubuntu session, such as being able to format the internal drives.
I would like to add a Guest user that is exactly the same as the Guest user in a Full install, No power to do anything destructive and a full cleansing of the Guest account after every use.