We know it is deprecated but there are still systems that are running Debian 8, or at least applications that used old packages such as PHP 5 that you may need an environment to stage testing/updates for it.
deb http://archive.debian.org/debian/ jessie main contrib non-free
deb http://archive.debian.org/debian-security jessie/updates main contrib non-free
If you are in Docker there is no vi/nano or editor so you need to echo into it:
echo "deb http://archive.debian.org/debian/ jessie main contrib non-free
deb http://archive.debian.org/debian-security jessie/updates main contrib non-free" > /etc/apt/sources.list
If you need a basic LAMP setup then install these packages:
apt install vim php5-mysql libapache2-mod-php5 apache2 mysql-server wget