You can pull information via one or more environment variables by providing the name of the variable for a given containerName.

env:                              # Optional.
  - parameter: region             # Required - Defined by the scale trigger
    name: my-env-var              # Required.
    containerName: my-container   # Optional. Default: scaleTargetRef.envSourceContainerName of ScaledObject

Assumptions: containerName is in the same resource as referenced by in the ScaledObject, unless specified otherwise.