How to access environment variables with Cloudflare Pages/Workers?

Using Vue I’m trying to access some environment variables that contain sensitive data using process.env.ENV_VAR and it works locally but it doesn’t work with Cloudflare Pages, after reading their docs it seems I have to use fetch to access the env vars (https://developers.cloudflare.com/workers/configuration/environment-variables/) but I don’t quite understand how should I access the env vars, what I ended up doing is create a env_data.js file that should export the env vars, the file contains are:

let TURNSTILE_SITE_KEY;
let TURNSTILE_SECRET_KEY;

function fetch(request, env, ctx) {
    TURNSTILE_SITE_KEY = env.TURNSTILE_SITE_KEY;
    TURNSTILE_SECRET_KEY = env.TURNSTILE_SECRET_KEY;
}

fetch()

export default {
    TURNSTILE_SITE_KEY,
    TURNSTILE_SECRET_KEY
}

I import it with import env_data from "@/env_data.js"; and try to access the data with env_data.TURNSTILE_SITE_KEY but it doesn’t work as Cloudflare errors when building the functions:

 Error: Failed to publish your Function. Got error: Uncaught TypeError: Cannot read properties of undefined (reading 'TURNSTILE_SITE_KEY')
  at functionsWorker-0.5745917335237649.js:5:28 in fetch2
  at functionsWorker-0.5745917335237649.js:8:1

How should I access the environment variables?