The short answer for this is to apply GitOps deployment practices in your workflow.

1. All your Kubernetes YAMLs or Helmcharts are in a single git repository which is used by a GitOps operator.
2. In your CI pipeline, you only have to build and push docker images.
3. The GitOps operator intelligently fetches images versions and make changes and a commit to the target Kubernetes YAML in the repository.
4. Every change in the GitOps repository is applied to the cluster.

See https://fluxcd.io/

Did you know helm chart? It is designed for different environment deployment.

With different values.yaml file, you can quickly deploy to different environment with same source code base.

For example, you can name the values.yaml file with environment.

values-dev.yaml
values-sit.yaml
values-prod.yaml

the only differences are some varialbes, such as environment (dev/sit/prod), and namespaces.

so when you run the deployment, it will be:

env=${ENVIRONMENT}
helm install -f values-${env}.yaml myredis ./redis

So my question is:

How are you triggering these builds? Manually? GitHub Trigger? HTTP Trigger using the REST API?

so you're almost there for the building/pushing part, you would need to use substitution variables https://cloud.google.com/cloud-build/docs/configuring-builds/substitute-variable-values

If you would be triggering the builds manually, you would edit the build trigger and change the sub variable for what you want it to be. GitHub Trigger -- this is a little more complex as you might want to do releases or branches. HTTP Trigger, same as manual, in your request you change the sub variable.

So here's part of one of our repo build files, as you will see there are different sub. variables we use, sometimes we want to build the image AND deploy to cluster, other times we just want to build or deploy.

steps:
# pull docker image
- name: 'gcr.io/cloud-builders/docker'
  id: pull-docker-image
  entrypoint: 'bash'
  args:
  - '-c'
  - |
    docker pull ${_TAG_DOCKER_IMAGE} || exit 0

# build docker image
- name: 'gcr.io/cloud-builders/docker'
  id: build-docker-image
  entrypoint: 'bash'
  args:
  - '-c'
  - |
    if [[ "${_BUILD_IMAGE}" == "true" ]]; then
       docker build -t ${_DOCKER_IMAGE_TAG} --cache-from ${_TAG_DOCKER_IMAGE} .;
    else
       echo "skipping ... BUILD_IMAGE=${_BUILD_IMAGE}";
    fi

# push docker image
- name: 'gcr.io/cloud-builders/docker'
  id: push-docker-image
  entrypoint: 'bash'
  args:
  - '-c'
  - |
     if [[ "${_BUILD_IMAGE}" == "true" ]]; then
        docker push ${_DOCKER_IMAGE_TAG};
     else
        echo "skipping ... BUILD_IMAGE=${_BUILD_IMAGE}";
     fi

# tag docker image
- name: 'gcr.io/cloud-builders/gcloud'
  id: tag-docker-image
  entrypoint: 'bash'
  args:
  - '-c'
  - |
    if [[ "${_BUILD_IMAGE}" == "true" ]]; then
       gcloud container images add-tag ${_DOCKER_IMAGE_TAG} ${_TAG_DOCKER_IMAGE} -q;
    else
       echo "skipping ... BUILD_IMAGE=${_BUILD_IMAGE}";
    fi


# update service image on environment
- name: 'gcr.io/cloud-builders/kubectl'
  id: update service deployment image
  entrypoint: 'bash'
  args:
  - '-c'
  - |
    if [[ "${_UPDATE_CLUSTER}" == "true" ]]; then
       /builder/kubectl.bash set image deployment $REPO_NAME master=${_DOCKER_IMAGE_TAG} --namespace=${_DEFAULT_NAMESPACE};
    else
       echo "skipping ... UPDATE_CLUSTER=${_UPDATE_CLUSTER}";
    fi
  env:
  - 'CLOUDSDK_COMPUTE_ZONE=${_CLOUDSDK_COMPUTE_ZONE}'
  - 'CLOUDSDK_CONTAINER_CLUSTER=${_CLOUDSDK_CONTAINER_CLUSTER}'


# subs are needed because of our different ENVs
# _DOCKER_IMAGE_TAG = ['gcr.io/$PROJECT_ID/$REPO_NAME:gcb-${_COMPANY_ENV}-$SHORT_SHA', 'other']
# _COMPANY_ENV = ['dev', 'staging', 'prod']
# _DEFAULT_NAMESPACE = ['default'] or ['custom1', 'custom2']
# _CLOUDSDK_CONTAINER_CLUSTER = ['dev', 'prod']
# _CLOUDSDK_COMPUTE_ZONE = ['us-central1-a']
# _BUILD_IMAGE = ['true', 'false']
# _UPDATE_CLUSTER = ['true', 'false']
substitutions:
    _DOCKER_IMAGE_TAG: $DOCKER_IMAGE_TAG
    _COMPANY_ENV: dev
    _DEFAULT_NAMESPACE: default
    _CLOUDSDK_CONTAINER_CLUSTER: dev
    _CLOUDSDK_COMPUTE_ZONE: us-central1-a
    _BUILD_IMAGE: 'true'
    _UPDATE_CLUSTER: 'true'
options:
    substitution_option: 'ALLOW_LOOSE'
    env:
    - _TAG_DOCKER_IMAGE=gcr.io/$PROJECT_ID/$REPO_NAME:${_COMPANY_ENV}-latest
    - DOCKER_IMAGE_TAG=gcr.io/$PROJECT_ID/$REPO_NAME:gcb-${_COMPANY_ENV}-$SHORT_SHA
tags:
- '${_COMPANY_ENV}'
- 'build-${_BUILD_IMAGE}'
- 'update-${_UPDATE_CLUSTER}'

we have two workflows --

1. github trigger builds and deploys under the 'dev' environment.
2. we trigger via REST API https://cloud.google.com/cloud-build/docs/api/reference/rest/v1/projects.builds/create (we replace the variables via the request.json) -- this method also works using the gcloud builds --substitutions CLI.

Hope that answers your question!