apiVersion: v1
kind: ReplicationController
metadata:
  labels:
    k8s-app: heapster
    name: heapster
    version: v6
  name: heapster
  namespace: kube-system
spec:
  replicas: 1
  selector:
    k8s-app: heapster
    version: v6
  template:
    metadata:
      labels:
        k8s-app: heapster
        version: v6
    spec:
      containers:
      - name: heapster
        image: kubernetes/heapster:canary
        imagePullPolicy: Always
        command:
        - /heapster
        - --source=kubernetes:https://kubernetes.default
        - --sink="kafka:?brokers=monitoring-kafka:9092&timeseriestopic=timeseries&eventstopic=events"

apiVersion: v1
kind: ReplicationController
metadata:
  labels:
    k8s-app: heapster
    name: heapster
    version: v6
  name: heapster
  namespace: kube-system
spec:
  replicas: 1
  selector:
    k8s-app: heapster
    version: v6
  template:
    metadata:
      labels:
        k8s-app: heapster
        version: v6
    spec:
      containers:
      - name: heapster
        image: kubernetes/heapster:canary
        imagePullPolicy: Always
        command:
        - /heapster
        - --source=kubernetes:https://kubernetes.default
        - --sink=kafka:?brokers=monitoring-kafka:9092&timeseriestopic=timeseries&eventstopic=events

Remove quoting around --sink argument
Remove quoting around --sink argument

after two days of debugging why we're not getting any metrics, we tried removing the quotes around the --sink argument and it started working.