Because your minikube is running on a virtual machine on your laptop , you just need minikube ssh into that machine and enter the address of your external service into the /etc/hosts file of that virtual machine.

Create Endpoints that will forward traffic to your desire external IP address (your local machine). You can directly connect using Endpoints but according to Goole Cloud best practice (doc) is to access it through a Service

Create your Endpoints

kind: Endpoints
apiVersion: v1
metadata:
 name: local-ip
subsets:
 - addresses:
     - ip: 10.240.0.4  # IP of your desire end point
   ports:
     - port: 27017     # Port that you want to access

Then create you Service

kind: Service
apiVersion: v1
metadata:
 name: local-ip
Spec:
 type: ClusterIP
 ports:
 - port: 27017
   targetPort: 27017

Now you can call external http service using the Service name. In this case loal-ip like any other internal service of minikube.