As I prototype and build new applications, I frequently use a couple tricks for quickly setting up new app data:
Make sure new Sheets are organized in protected folders to easily find it in the future and avoid accidentally breaking your app data structure while revising other sheets.
Mock data can be tedious to create while prototyping - Mockaroo.com is a useful, free tool for quickly generating random data in your tables.
(New Tricks!) To elaborate on the quick Google Doc links listed above, I’ve recently started using some custom URLs to quickly generate new documents automatically saved in a specific Google Drive folder (open your destination folder to find the ID in the URL bar):
These URLs work great as Virtual Column actions in your applications - I use them for quickly generating shared docs associated with meetings related to a project management app.