Which of the following solutions would not meet the goal of allowing Docker containers to access Azure SQL databases via a subnet service endpoint?

Creating an application security group does not facilitate access for Docker containers to Azure SQL databases through a subnet service endpoint. An application security group is used to manage and enforce security policies on virtual machines within a virtual network. While they are useful for controlling network security and defining rules, they do not directly manage the routing or access to Azure SQL databases via service endpoints.

In contrast, configuring a virtual network gateway allows for the establishment of secure connections between Azure and on-premises networks, which is essential for certain architectural setups but does not specifically address service endpoint access for containers. Installing the container network interface (CNI) plug-in is crucial for enabling Docker containers to integrate with Azure Virtual Networks, allowing them to communicate with other services, including Azure SQL databases when service endpoints are in use. Setting service endpoint policies is directly related to defining access permissions for Azure resources over service endpoints, making it a vital option for the stated goal.

By focusing on the role of application security groups, it's clear that their primary function is for security management of VM traffic rather than enabling direct database connectivity for containerized applications using service endpoints.