Amazon EC2 now supports tagging EC2 Spot Instance requests
Amazon EC2 Spot Instances let you take advantage of unused Amazon EC2 capacity. Spot Instances are available at up to a 90% discount compared to On-Demand prices. You can use Spot Instances for various stateless, fault-tolerant, or flexible applications such as big data, containerized workloads, CI/CD, web servers, high-performance computing (HPC), and other test & development workloads. Starting today, you can assign AWS resource tags to Spot Instance requests on creation, in addition to the tags for each individual, launched Spot Instance.. Use tags in your Spot Instance requests to more easily identify their purpose. For example, you can use tags to identify all Spot Instance requests used by a particular department, project, or application.
Source:: Amazon AWS