Sudo minikube returns “command not found”

Try using Disk Utility to repair file permissions -- with any luck, that should reset the setuid bit on the /usr/bin/sudo that you copied. It's a flag that lets sudo act as root even when it's not run as root, which obviously it needs to be able to do, but you'll need sudo to set it using the command line so you have a chicken-and-egg problem.

$PATH is evaluated by your shell, so your check doesn't work as you expect it to.

/etc/sudoers is configured to replace your PATH with a default one.

sudo does not load a login shell environment before executing the command, so the default PATH from /etc/sudoers is used. su - does open a login shell, which involves loading /etc/profile. See man bash, section INVOCATION.

Just remove the PATH reset in /etc/sudoers. It's likely a rule called secure_path.

CentOS

In CentOS you can add PATH to the Defaults env_keep section:

Defaults    env_keep = "COLORS DISPLAY HOSTNAME HISTSIZE INPUTRC KDEDIR \
                        LS_COLORS MAIL PS1 PS2 QTDIR USERNAME \
                        LANG LC_ADDRESS LC_CTYPE LC_COLLATE LC_IDENTIFICATION \
                        LC_MEASUREMENT LC_MESSAGES LC_MONETARY LC_NAME LC_NUMERIC \
                        LC_PAPER LC_TELEPHONE LC_TIME LC_ALL LANGUAGE LINGUAS \
                        _XKB_CHARSET XAUTHORITY PATH"