deployment.yaml

apiVersion: v1
kind: Namespace
metadata:
  name: samples
---
apiVersion: v1
kind: ConfigMap
metadata:
  name: sample-api-cm
  namespace: samples
data:
  SAMPLE__ENV1: val1
  SAMPLE__ENV2: val2
  SECTION__ONE: k8s
---
apiVersion: apps/v1beta2
kind: Deployment
metadata:
  name: sample-api-dep
  namespace: samples
  labels:
    app: sample-api-app
spec:
  replicas: 3
  selector:
    matchLabels:
      app: sample-api-app
  # wait 3 seconds before starting new instance/replica
  minReadySeconds: 3
  strategy:
    type: RollingUpdate
    rollingUpdate:
      maxSurge: 30%
      maxUnavailable: 30%
  template:
    metadata:
      annotations:
        kubernetes.io/change-cause: "First Deployment"
      labels: 
        app: sample-api-app
    spec: 
      containers:
      - name: sample-api-container
        image: gIMAGES
        imagePullPolicy: Always
        ports:
        - containerPort: 80
        # works
        env:
        - name: SAMPLE__ENV1
          valueFrom:
            configMapKeyRef:
              name: sample-api-cm
              key: SAMPLE__ENV1
        - name: SAMPLE__ENV2
          valueFrom:
            configMapKeyRef:
              name: sample-api-cm
              key: SAMPLE__ENV2
        # does not. comment out above etc
        envFrom:
        - configMapRef:
          name: sample-api-cm

Here is a fix:

         envFrom:
         - configMapRef:
-          name: sample-api-cm
+            name: sample-api-cm