How to backup wordpress website when digital ocean droplet is full?

Basically, you can

Upgrading the machine: 

1. Upgrade the machine to a higher configuration which has more volume, moved RAM and better processor
2. This will move all the disk data to the new machine without any issues.
3. Now that you have more space you can use any WordPress backup plugin to backup, download, and upload (if you are a dev, you can use wget for faster transfer)

Incremental Backup 

1. Take the smallest (in terms of space consumed on disk), make backup, and move
2. Take the next smallest and do the same
3. Repeat until you get to the biggest site and you will have enough space to back and move

Fuzzy and time-consuming way

1. Backing up the database from phpmyadmin or SQL command and downloading the file
2. For file, Using connecting filezilla using SSH or FTP and backing up the file

Note: Unzipped file takes quite good amount of time to be downloaded. Be patient, and ensure that you have continuous internet and power backup for smoother transfer.