Make an input box compare its input to a discrete website text

So I have an app that lets me share photographs of my local sports club when they play matches. The app is on play store but I only want certain people to have access. I have made a password style system by comparing text input to a string i created but I want to be able to change this string remotely without doing an app update.Can I use google spreadsheets or a style website that has a discrete link and contains the password and the app checks this website for login?

Many thanks