The hot deals collection that you see in our mobile application is a collection that is built on the special price functionality of the core Magento.
In order to add a product to this collection, all you need to do is open the product in your admin panel and set the attributes for Special Price, Special Price From Date and Special Price To Date(refer to the highlighted region in the screenshot).
Here we can have three cases with respect to Special Price Date-
Case 1- Here, both Special Price From Date and Special Price To Date is mentioned which states that this product will be in hot deals section from a specific date to a specific date.
Case 2- Here, only Special price From date is filled which will make a product visible in Hot Deals section from the stated date till current date or forever.
Case 3- Here only Special Price To Date is mentioned, which will make the products visible in the hot deals till the specified date.
After you have set these attribute from your admin panel, then a collection using this is built through the code to be displayed in your application.
If the collection has more than 5 products, then 5 products in a random order are selected and displayed on the home page of your application, like in the image below :