Using "Expect"

[ ! -e /usr/bin/expect ] && { apt-get -y install expect; }
SECURE_MYSQL=$(expect -c "

set timeout 10
spawn mysql_secure_installation

expect \"Press y|Y for Yes, any other key for No: \"
send \"n\r\"
expect \"Change the password for root ? ((Press y|Y for Yes, any other key for No) : \"
send \"n\r\"
expect \"Remove anonymous users? (Press y|Y for Yes, any other key for No) : \"
send \"y\r\"
expect \"Disallow root login remotely? (Press y|Y for Yes, any other key for No) : \"
send \"y\r\"
expect \"Remove test database and access to it? (Press y|Y for Yes, any other key for No) : \"
send \"y\r\"
expect \"Reload privilege tables now? (Press y|Y for Yes, any other key for No) : \"
send \"y\r\"
expect eof
")

echo "$SECURE_MYSQL"