Sublime Text can be reverted to a freshly installed state by removing your data folder. Depending on your operating system, this folder is located in:
OS X: ~/Library/Application Support/Sublime Text 3
Windows: %APPDATA%\Sublime Text 3
To revert to a freshly installed state, you can:
Exit Sublime Text
Delete (or move) the data folder, as listed above
Start Sublime Text
When restarted, a fresh data folder will be created, just as it was the first time you ran Sublime Text. Keep in mind that this will also remove all of your settings and packages.
OS X Lion
In Lion, the ~/Library folder is hidden by default. To navigate there, select the Go/Go to Folder menu item in Finder, and type in ~/Library.
In Windows, cache files are stored in a separate location, %LOCALAPPDATA%\Sublime Text 3, to improve performance with roaming profiles.