Accidentally deleted tmp folder

I can't think of a reason why this shouldn't work. On my system, the permissions are set by:

sudo chmod 1777 /tmp

(drwxrwxrwxt)

You should run the following commands to restore the tmp folder.

sudo -i
# You now have a root prompt and do not need to continue typing sudo
mkdir /tmp
chmod 1777 /tmp
exit

Then you sould be all good

To add to Alex's answer, you can do both those commands at the same time using the -m or --mode option for mkdir(1), which specifies the mode for the created directory:

-m, --mode=MODE   set file mode (as in chmod), not a=rwx - umask

So the command would be:

sudo mkdir -m 1777 /tmp