#--> first identify your USB disk:

fdisk list

# --> Example OUTPUT
: '
/dev/disk0 (internal, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *1.0 TB     disk0
   1:                        EFI EFI                     209.7 MB   disk0s1
   2:                 Apple_APFS Container disk1         1.0 TB     disk0s2

/dev/disk1 (synthesized):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      APFS Container Scheme -                      +1.0 TB     disk1
                                 Physical Store disk0s2
   1:                APFS Volume Macintosh HD - Datos    907.8 GB   disk1s1
   2:                APFS Volume Preboot                 81.5 MB    disk1s2
   3:                APFS Volume Recovery                526.6 MB   disk1s3
   4:                APFS Volume VM                      2.1 GB     disk1s4
   5:                APFS Volume Macintosh HD            11.0 GB    disk1s5

/dev/disk2 (external, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:     Apple_partition_scheme                        *248.7 GB   disk2
   1:        Apple_partition_map                         4.1 KB     disk2s1
   2:                  Apple_HFS                         4.1 MB     disk2s2
'

#--> in this example USB stick is disk2 (external, physical):

# --> let's blank complete pendrive:

sudo dd if=/dev/zero of=/dev/disk2 count=1 bs=4096

# --> let's check again:

diskutil list

: '
/dev/disk0 (internal, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *1.0 TB     disk0
   1:                        EFI EFI                     209.7 MB   disk0s1
   2:                 Apple_APFS Container disk1         1.0 TB     disk0s2

/dev/disk1 (synthesized):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      APFS Container Scheme -                      +1.0 TB     disk1
                                 Physical Store disk0s2
   1:                APFS Volume Macintosh HD - Datos    907.8 GB   disk1s1
   2:                APFS Volume Preboot                 81.5 MB    disk1s2
   3:                APFS Volume Recovery                526.6 MB   disk1s3
   4:                APFS Volume VM                      2.1 GB     disk1s4
   5:                APFS Volume Macintosh HD            11.0 GB    disk1s5

/dev/disk2 (external, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:                                                   *248.7 GB   disk2
'

# Then you can run disk utility to initialize / format pendrive.