I just stumbled across a way to disable cache in Safari on iOS:
iOS
- Open Settings
- Navigate to Safari > Advanced
- Enable Web Inspector
- Switch back to Safari and load a web page
Desktop
- Open Safari
- Navigate to Safari > Preferences > Advanced tab
- Enable the Develop menu
- In the Develop menu, select Your iOS Device Name > The Page You Want to Debug
- Press Command-Shift-R to reload while disabling cache
- Bonus: This is a full Web Inspector on your computer inspecting a page on your iOS device
If you want something more permanent, you’ll either have to go the proxy route or make a UIWebView/WKWebView wrapper app that disables caching.