Defining Products in scripts
You can declare your Product list programmatically using the Purchasing Configuration Builder. You must provide a unique cross-store Product ID and Product Type for each Product:
using UnityEngine;
using UnityEngine.Purchasing;
public class MyIAPManager {
    public MyIAPManager () {
        var builder = ConfigurationBuilder.Instance(StandardPurchasingModule.Instance());
        builder.AddProduct("100_gold_coins", ProductType.Consumable);
        // Initialize Unity IAP...
    }
}