My iPhone 7 gets overheated and drains its battery rapidly

Below are additional factors to consider when your battery has started draining more quickly. I recommend you read through and follow suggestions in the Apple support articles linked to at the bottom of this response.

iPhone Battery Capacity

Go to Battery section in the Settings app:

• What does it report as your maximum capacity?
• What does it report under Peak Performance Capability?
• Are either different than before your problems started?

iOS Update:

• Did you recently update the iOS before the battery drainage problem started?

Updates to an iOS, especially to a major version (iOS 12.X –> iOS 13.X), can cause battery problems even in newer iPhones. If your phone’s been used for a few years and already has decreased battery capacity, you are more likely to experience (at least temporary) more rapid battery drainage.

Here are relevant Apple Support articles on understanding iPhone Battery and Performance and Maximizing Battery Performance

If the problem continues after trying the steps in the articles, I recommend directly contacting Apple Support

I hope these resources will help you find a way to reduce your iPhone’s rapid battery drainage.

Another consideration:

How long you have/used your iPhone 7? The longer (months, years), more often you use an iPhone, the more quickly the battery capacity (amount of charge it can hold) decreases. In other words, an older battery cannot hold as much of a charge as a new battery.

The more frequently you need to recharge the battery (as its capacity declines), also contributes to the decrease in capacity. It is kind of a vicious cycle, but it’s how that type of battery works.

You should be able to find your current battery capacity in the Settings app from iOS 11.0 onward.

Most probably it's from the battery, which should be changed or maybe because your storage is full or a heavy app on your phone like a game (pubg or fortnite)