[throwaway2048]

    env_reset    
        
    If set, sudo will run the command in a minimal
    environment containing the TERM, PATH, HOME, MAIL,
    SHELL, LOGNAME, USER, USERNAME and SUDO_* variables.
    Any variables in the caller's environment that match
    the env_keep and env_check lists are then added,
    followed by any variables present in the file specified
    by the env_file option (if any).  The default contents
    of the env_keep and env_check lists are displayed when
    sudo is run by root with the -V option.  If the
    secure_path option is set, its value will be used for
    the PATH environment variable.  This flag is on by
    default.

Also this would open up an entire vector of arbitrary command execution attacks if it was allowed.

Also, you can not use LD_PRELOAD on sudo itself, as it is disabled for setuid binaries.