I have a crontab running every hour. The user running it has environment variabless in the .bash_profile that work when the user runs the job from the terminal,
.bash_profile
sudo sh -c "echo MY_GLOBAL_ENV_TO_MY_CURRENT_DIR=$(pwd)" >> /etc/environment"
crontab -e */5 * * * * sh -c "$MY_GLOBAL_ENV_TO_MY_CURRENT_DIR/start.sh"
=)