The following sample script shows how you can run drush commands in branch container...
$ cat run_command_in_a_running_branch.sh
#!/bin/bash
JWT_TOKEN=`cat JWT_TOKEN.txt`
AUTH_HEADER="authorization: Bearer $JWT_TOKEN"
ORGANIZATION_HEADER="tenant: api-1620640441-org"
curl -s -X POST \
'https://api.site.devpanel.com/dev-v1/sites/60993039c25947001370c/branches/6099303bc25947001370c/commands' \
-H 'cache-control: no-cache' \
-H 'content-type: application/json' \
-H 'auth-mode: cognito' \
-H "$AUTH_HEADER" \
-H "$ORGANIZATION_HEADER" \
--data-raw '{ "commands": ["drush", "status"] }' | jq -r ".result" Drupal version : 9.1.7
Site URI : http://default
Database driver : mysql
Database hostname : devpanel-cluster-vvybh.cso9f6tlh.us-west-2.rds.amazonaws.com
Database port :
Database username : useroqnj
Database name : nameoqnj
Database : Connected
Drupal bootstrap : Successful
Drupal user :
Default theme : bartik
Administration theme : seven
PHP executable : /usr/local/bin/php
PHP configuration :
PHP OS : Linux
Drush script : /home/www/.composer/vendor/drush/drush/drush.php
Drush version : 8.4.8
Drush temp directory : /tmp
Drush configuration :
Drush alias files :
Install profile : standard
Drupal root : /var/www/html/web
Drupal Settings File : sites/default/settings.php
Site path : sites/default
File directory path : sites/default/files
Sync config path : sites/default/files/config_LDffgk-brK4SAoRoc7UC_QPMfg4LNBi6_8_7hOSuhPT_UHmM7d-IYwiMQlu_u9m0s/sync