The theme cache should be rebuilt whenever you make a change to your code and save it. Adding a line break somewhere safe (like after an existing line break) in your theme.liquid and saving would achieve this.
I get the sense though it's probably not a cache issue. Would you have any more details about what problem you're experiencing?
Ted here from Shopify, thanks for reaching out to us.
As previously mentioned by @Alex_Lam and @Reincarnated, the store's cache should be auto clearing/rebuilt when theme changes are made. Are you seeing an error on your store? If so, could you show me an example of what's happening?
If there is anything else I can help you with, please let me know, I'm happy to take a closer look.
Hey Arbaz, for scaled images, that means your site isn't using responsive image sizes. The right sized image isn't being loaded for the size of the container on your site. Here's a guide from Shopify on how to add that! https://www.shopify.ca/partners/blog/using-responsive-images
Or if you're looking for help, our app Hyperspeed can add responsive sizes to your theme images - https://apps.shopify.com/hyperspeed