show account chooser every time with GoogleSignInApi

The account selection is cached, so you have to call signOut first.

Call signOut on GoogleApiClinet.

Where ever you are calling this code

Auth.GoogleSignInApi.getSignInIntent(mGoogleApiClient);

Write this code before that.

Auth.GoogleSignInApi.signOut(mGoogleApiClient);

So your new code will look line

Auth.GoogleSignInApi.signOut(mGoogleApiClient);
Intent signInIntent = Auth.GoogleSignInApi.getSignInIntent(mGoogleApiClient);
startActivityForResult(signInIntent, RC_SIGN_IN);

Now it will open popup again & again