How to apply plugin to only one flavor in gradle?

Use this code:

if (!getGradle().getStartParameter().getTaskRequests()
        .toString().contains("Develop")){
    apply plugin: 'com.google.gms.google-services'
}

getGradle().getStartParameter().getTaskRequests().toString() returns something like [DefaultTaskExecutionRequest{args=[:app:generateDevelopDebugSources],projectPath="null"}] so as stated in the comments Develop must start with an uppercase.