Hellooo!! I describe the work without naming the client or using internal project names or terminology.
So rather than: "I worked on the XYZ project/case/deal for XYZ, which included XYZ"
I’d say: "I worked on a network infrastructure upgrade across a hospitality company's portfolio. This involved presenting to stakeholders at different levels and scheduling engineers across multiple sites. As a result, I achieved XYZ."
It still shows the scale, the sector and your impact without giving anything confidential away. Unless someone digs into your employer, that client could be ANYONE.