that is because cron doesn’t run under your user profile (sudo does the same) – hence it cannot find the AWS settings, including $path and all other AWS stuff.
put all the AWS settings in .profile, for example, and then in front of the the croned script, just include “$HOME/.profile;”

like:
* * * * * $HOME/.profile; /path_to_aws_script/dailybackup

or include the variables in the script itself.

Hope this helps.