In your application pod write logs to path in filesystem using a volumeMounts.

From the docs here use a sidecar container with a logging agent such as fluentbit to send logs written to the filesystem to a centralized logging backend such as splunk or Elasticsearch.

  apiVersion: apps/v1
  kind: Deployment
  metadata:
    name: fluentbit-logging-sidecar
  spec:
    selector:
      matchLabels:
        app: fluentbit-logging-sidecar
    replicas: 1
    template:
      metadata:
        labels:
          app: fluentbit-logging-sidecar
        volumes:
          - name: shared-data
            emptyDir: {}
          - name: config-volume
            configMap:
              name: fb-agent-config
        containers:
          - name: sample-logging
            image: <image>
            volumeMounts:
            - name: shared-data
              mountPath: /app/logs
          - name: fb-sidecar
            image: fluent/fluent-bit  
            volumeMounts:
            - name: shared-data
              mountPath: /app/logs
            - name: config-volume
              mountPath: /fluent-bit/etc/fluent-bit.conf
              subPath: fluent-bit.conf