From the sudo man page
-i, --login
Run the shell specified by the target user's password database entry as a login shell. This means that login-specific resource files such
as .profile or .login will be read by the shell. If a command is specified, it is passed to the shell for execution via the shell's -c
option. If no command is specified, an interactive shell is executed. sudo attempts to change to that user's home directory before running
the shell. The command is run with an environment similar to the one a user would receive at log in. The Command environment section in
the sudoers(5) manual documents how the -i option affects the environment in which a command is run when the sudoers policy is in use.
So it seems likely that this will be coming from something to do with the www-data account.
I would start by looking in the passwd file for the www-data user entry and working on from there.