Employ ProGuard to obfuscate

build.gradle

buildTypes {
        release {
            buildConfigField "String", "BASE_URL", "\"https://mbl.test.com\""
            minifyEnabled true
            shrinkResources true
            debuggable false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'),
                                                       'proguard-rules.pro'
        }