How to "deploy" in kubernetes without any changes, just to get pods to cycle

According to documentation:

Note: a Deployment’s rollout is triggered if and only if the Deployment’s pod template (i.e. .spec.template) is changed, e.g. updating labels or container images of the template.

You can just use kubectl patch to update i.e. a label inside .spec.template.

As of kubectl 1.15, you can run:

kubectl rollout restart deployment <deploymentname>

What this does internally, is patch the deployment with a kubectl.kubernetes.io/restartedAt annotation so the scheduler performs a rollout according to the deployment update strategy.

For previous versions of Kubernetes, you can simulate a similar thing:

 kubectl set env deployment --env="LAST_MANUAL_RESTART=$(date +%s)"  "deploymentname"

And even replace all in a single namespace:

 kubectl set env --all deployment --env="LAST_MANUAL_RESTART=$(date +%s)" --namespace=...