There's no reliable public list of IP addresses for Starbucks Wi-Fi, nor is there any reliable way to determine if an IP address corresponds to Starbucks Wi-Fi.
After Starbucks (at least in the US) switched from AT&T to Google for Wi-Fi service, Google has been providing the service via any available ISP, whether Google owned or not.
For example, the local Starbucks Wi-Fi provided by Google is run on a Comcast Business cable connection. There's no way to distinguish its IP address from any other Comcast Business customer.
Therefore, in order to ban Starbucks customers, you will need a fairly large IP address range:
If you block this range, it's guaranteed to block all Starbucks customers. (And everyone else.)