Depends on the platform where you running Kubernetes (on-premises, AWS, GKE, GCE etc.) you have several ways to do it, but I will describe a solution which will work on all platforms - Ingress with HTTPS termination on it.

So, in Kubernetes you can provide access to your application inside a cluster using Ingress object. It can provide load balancing, HTTPS termination, routing by path etc. In most of the cases, you can use Ingress controller based on Nginx. Also, it providing TCP load balancing and SSL Passthrough if you need it.

For providing routing from users to your services, you need:

1. Deploy your application as a combination of Pods and Service for them.
2. Deploy Ingress controller, which will manage your Ingress objects.
3. Create a secret for your certificate.
4. Create an Ingress object with will point to your service with TLS settings for ask Ingress to use your secret with your certificate, like that:

spec: tls: hosts: - foo.bar.com secretName: foo-secret

5. Now, when you call the foo.bar.com address, Ingress with using FQDN-based routing and provide HTTPS connection between your client and pods in a cluster using a service object, which knows where exactly your pod is. You can read how it works here and here.

What about encrypted communication between your services inside a cluster - you can use the same scheme with secrets for providing SSL keys to all your services and setup Service to use HTTPS endpoint of an application instead of HTTP. Technically it is same as using https upstream in installations without Kubernetes, but all configuration for Nginx will be provided automatically based on your Service and Ingress objects configuration.