Apple - sudo: command not found
Your PATH is hosed!
First check your .bash_profile file with:
/usr/bin/nano ~/.bash_profile
Prepend lines containing something like export PATH="/... "
with a #
to comment them out. Save the file with ctrlO and exit nano with ctrlX
Then check /etc/paths with: /bin/cat /etc/paths
.
It should look like this:
/usr/local/bin
/usr/bin
/bin
/usr/sbin
/sbin
You can edit the file with /usr/bin/sudo /usr/bin/nano /etc/paths
if required.
If everything is fine enter source ~/.bash_profile
or close the Terminal window and open a new one.
Now sudo should work again. Then check all #export PATH=...
lines in your .bash_profile for potential errors. You may add them to your question to get help here.