How to pass all values from multiple Secrets to env variables in Kubernetes?

Try using one envFrom with multiple entries under it as below:

      - name: integration-app
        image: my-container-image
        envFrom:
        - secretRef:
            name: intercom-secret
        - secretRef:
            name: paypal-secret
        - secretRef:
            name: postgres-secret
        - secretRef:
            name: redis-secret

There’s an example at the bottom of this blog post by David Chua