If sidecar injection is enabled for a namespace of a cluster, sidecars are automatically injected for the pods of all workloads in the namespace. To prevent sidecars from being injected for some workloads, perform the following operations:
annotations:
sidecar.istio.io/inject: 'false'

Locate the spec.template.metadata.label field and add sidecar.istio.io/inject: 'false'.
label:
sidecar.istio.io/inject: 'false'

For more details about sidecar injection, see Automatic Sidecar Injection.