Karlie here from the Shopify Guru Team! There are a couple of apps that I would recommend checking out, that have plenty of reviews and are recommended by other gurus! Be sure to check out: Sale Rack and Product Discount for a flash sale/daily deal type of app!
I hope this helps, but if you have any further questions - be sure to reach out to Shopify support!
Orangetwig is just the app you are looking for. It creates daily deal and sale templates for you which you can schedule as posts across your social channels.
Have a look at some of the templates
Get Started with Orangetwig for free
Hi Melanie, I recommend you check out Daily Deals. It allows you to create deals that last 24 hours, and it comes with countdown timers, and more. The deals automatically go back to their original price at midnight. It works great for this type of functionality :)
Instant Bulk Discount & Sales app exactly what you need. You can create a collection for daily deals products and then apply a discount to the collection in the app.
Unlike other discount apps, the Instant Bulk Discount & Sales app applies discounts for thousands of products in a few seconds. You don't need to wait for hours to activate discounts.