If you originally signed up with email + password you will see an option to change your email in the Milkshake App.
If you signed up using Apple, Google or Facebook sign in, the change email option is not available.
If you have signed to Milkshake with an email + password and you need to change your email, follow these steps:
Tap the Profile menu in the top right corner of the home screen
Tap Settings
Tap Change Email
Enter your new email address
Tap Continue
Your email should now be updated!