Of course, the easiest way would be to use rufus via windows but if you do not have a windows around, you need a different approach.
Under macOS there is balenaEtcher but for unknown reasons it doesn't detect the ESXi image as bootable and the result is not bootable either.

What's left is a manual approach, via terminal, that should work under macOS or Linux.
Below is a way to do this under macOS. Under linux is not that different: you need to use fdisk -l instead of diskutil list.

1. Format the USB stick as FAT32

I have named mine ESXI-7.

fmbp16:~ root# diskutil eraseDisk MS-DOS "ESXI" MBR disk2
Started erase on disk2 (ESXI-7.0U3L-21424296-STANDARD)
Unmounting disk
Creating the partition map
Waiting for partitions to activate
Formatting disk2s1 as MS-DOS (FAT) with name ESXI-7
512 bytes per physical sector
/dev/rdisk2s1: 120145216 sectors in 1877269 FAT32 clusters (32768 bytes/cluster)
bps=512 spc=64 res=32 nft=2 mid=0xf8 spt=32 hds=255 hid=2048 drv=0x80 bsec=120174592 bspf=14667 rdcl=2 infs=1 bkbs=6
Mounting disk
Finished erase on disk2

2. List the partition you just created and umount it:

fmbp16:~ root# diskutil list /dev/disk2

/dev/disk2 (external, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:     FDisk_partition_scheme                        *15.7 GB    disk2
   1:                 DOS_FAT_32 ⁨ESXI-7              15.7 GB    disk2s1
fmbp16:~ root# diskutil umountDisk /dev/disk2
Unmount of all volumes on disk2 was successful

3. Use fdisk to mark the partition active and make it bootable:

fmbp16:~ root# diskutil umountDisk /dev/disk2
Unmount of all volumes on disk2 was successful
fmbp16:~ root# fdisk -e /dev/disk2
fdisk: could not open MBR file /usr/standalone/i386/boot0: No such file or directory
Enter 'help' for information
fdisk: 1> f 1
Partition 1 marked active.
fdisk:*1> write
Writing MBR at offset 0.
fdisk: 1> exit

Also, mount back up the partition:

fmbp16:~ florian$ diskutil mount /dev/disk2s1
Volume ESXI-7 on /dev/disk2s1 mounted

4. Mount the ISO installer from vmware website and copy the content to USB partition:

fmbp16:~ root# cp -R /Volumes/ESXI-7.0B-16324942-STANDARD/* /Volumes/ESXI-7/

5. Now you need to modify ISOLINUX.CFG to point the boot to the right partition:

fmbp16:~ root# cd /Volumes/ESXI-7/
fmbp16:ESXi root# cat ISOLINUX.CFG | grep APPEND
  APPEND -c boot.cfg
fmbp16:ESXi root# sed -i "" 's/APPEND -c boot.cfg/APPEND -c boot.cfg -p 1/g' ISOLINUX.CFG
fmbp16:ESXi root# cat ISOLINUX.CFG | grep APPEND
  APPEND -c boot.cfg -p 1

And that is pretty much it. Unmount the partition and use it. It should be bootable on both sides: BIOS and EFI.