It’s not up to the ‘client’. They are users of your application, and you are responsible for setting the terms and conditions of using your application. As long as you are open and honest with your users regarding such conditions, you won’t have any issues.
In this case, it really is a technical limitation that you just shouldn’t be trying to fix with hacks that will cause your application more harm than good in the long run.
You can always add a notification in your application, such as “No internet connection detected. An active internet connection is required to receive your bonus 100 coins!”, or something similar. How you word it and display it is up to you. If users ask you why they need to connect to the internet, simply state the truth, which is that there is no way to verify their subscription without it.