buildTypes {
        release {
            applicationIdSuffix ".release"
            resValue "string", "app_name", "@string/app_name_release"
        }
        debug {
            applicationIdSuffix ".debug"
            resValue "string", "app_name", "@string/app_name_debug"
        }
 

<resources>

  <string name="app_name_release">Release</string>

  <string name="app_name_debug">Debug</string>

</resources>

<application

  android:label="@string/app_name"