Why doesn't the variable work in ssh inside a bash script?

Question

linux

I'm trying to create a file on the server using data from a variable

#!/bin/bash

nginx_default_page="server {
  listen 80;
  listen [::]:80;

  location / {
    proxy_pass http://127.0.0.1:3000;
  }

  error_page 500 502 503 504 /custom_50x;

  location = /custom_50x {
    root /usr/share/nginx/html;
    default_type application/json;
    internal;
  }
}
"

ssh $user@$host << 'ENDSSH'
echo "$nginx_default_page" | sudo tee /etc/nginx/conf.d/default.conf
ENDSSH

The variable is in quotes to preserve the formatting (otherwise everything is in a string). Is it possible in another way, or does it not affect?
An empty file is created default.conf. Why, how to fix?

Answer 1

VAR="blablabla
blablabla"

echo "$VAR" | ssh $user@$host 'cat>/tmp/file'
ssh $user@$host "sudo cp /tmp/file /etc;rm /tmp/file"

Answer 2

something like:
ssh [email protected]$host bash -c 'echo $моя_переменная'

Answer 3

Why, how to fix?

Because only selected environment variables are passed to the remote machine in an ssh session.
Copy a complex script in its entirety - it will be easier to debug.