How to clear/refresh cache

I’ve been tweaking some sidebars and I’ve found that each time I load a page with a sidebar, it gets “fixed” in that state. Then if I make edits to the sidebar, the version on that page doesn’t change when it’s reloaded. But loading a different page (which is assigned the same sidebar) shows the new version.

How do I clear or refresh the cache of all sidebars (I assume this is a cache thing)? Clearing my browser cache has no effect.