Insert Environment Variable using Jinja in SaltStack

Question

I am trying to read a JSON file inside a folder. using import_json. Here is my code

{% set instance_id = grains['INSTANCE_ID'] %}
INSTANCE_ID Env Var:
  environ.setenv:
    - name: INSTANCE_ID
    - value: {{ grains['INSTANCE_ID'] }}
    - update_minion: True

{% import_json "/tmp/$INSTANCE_ID/conf.json" as config_properties %}

But I am getting this error

Data failed to compile:
Rendering SLS 'base:cloud.steps.conf' failed: Jinja error: /tmp/$INSTANCE_ID/conf.json.

Although when I insert the INSTANCE_ID manually it works as expected.

What I want is to be able to insert either $INSTANCE_ID or directly the grain value {{ grains['INSTANCE_ID'] }}

Can someone please help me with this? Thanks.