The following code works on the command line
mysql --user=\'myusername\' --password=\'mypassword\' --database=\'mydatabase\' --execute=\'DROP DATABASE myusername
This one worked, double quotes when $user and $password are outside single quotes. Single quotes when inside a single quote statement.
mysql --user="$user" --password="$password" --database="$user" --execute='DROP DATABASE '$user'; CREATE DATABASE '$user';'