First of all why not use process.env.HOST inside your spec files. Second if you want to test in different host then what i have been doing is.

1. Create a folder (eg: configFiles)

2. Inside this create json files like (eg: host1.json, host2.json)

3. Inside your json file (in host1.json)

   { "env": { "HOST" : "host1" } }

4. Inside your plugins folder edit index.js

   const fs = require('fs-extra'); const path = require('path');

   function getConfigurationByFile(file) { const pathToConfigFile = path.resolve( 'cypress/configFiles', ${file}.json );

   return fs.readJson(pathToConfigFile); }

   module.exports = (on, config) => { const file = config.env.host || 'host1';

   return getConfigurationByFile(file); };

5. Then while running you can use npm cypress run --env host=host1

This is a late answer but you can achieve this by creating the variable in Plugins (https://docs.cypress.io/guides/guides/environment-variables#Option-5-Plugins)

Documentation states:

// .env file
USER_NAME=aTester

/

// plugins/index.js
require('dotenv').config()

module.exports = (on, config) => {
  // copy any needed variables from process.env to config.env
  config.env.username = process.env.USER_NAME

  // do not forget to return the changed config object!
  return config
}

// integration/spec.js
it('has username to use', () => {
  expect(Cypress.env('username')).to.be.a('string')
})

Avoid wrapping your env file in env variable. By the way this should do the job with your file:

Cypress.env("env")["HOST"]