1. You are not limiting location services
Go to Settings > Privacy > Location services
Here you can see a complete list of apps that are using GPS to identify your location which might be useful for an app like “Find my iPhone”. But the rest of the apps don’t need GPS and are draining your iPhone’s battery.
2. Turn off Fetch New Data
Settings > Mail, Contacts, and Calendars > Fetch New Data > Manually
There are strong chances that your iPhone is fetching your e-mails, updating automatically for new mails, calendars reminders, and contacts update and it takes a lot of battery.
Read More : How To Prevent iPhone Battery Meltdowns
3. Turn Off Background App Refresh
The description it self is telling you what you need to do.
Settings > General > Background App Refresh > Toggle It Off or Individual Services/Apps Off
4. Turn Off Auto Updates
This phone automatically updates applications and downloads from iTunes & App Store. This can drain your phone’s battery life, it would be worth turning it off.
Settings > iTunes & App Stores > Toggle Updates Off
5. Screen Brightness
Settings > Wallpapers & Brightness > Tone it down a bit.
To minimize screen brightness, You have to flick up from the bottom of the screen, and while you’re at it, turn off Auto-Brightness.
6. Use Airplane Mode
Remember, when ever you’re in a low coverage zone, your battery will drain faster. Because your phone drains battery when searching for coverage.
Just swipe up to tape the airplane button
7. Turn Off Bluetooth and WiFi
Make sure you don’t use the cell network unless you have to. Switch off Wi-Fi and Bluetooth, when you’re not using them — because in background, apps and services will attempt to use your Wi-Fi. same in case of Bluetooth.
Swipe up to bring up the control centre then turn off the Wi-Fi and Bluetooth
8. Spot Light Search
Settings > General > Spotlight Search
Spotlight is the index of your iPhone , which uses batteries. You might not use it regularly
9. Turn Off AirDrop
This feature lets users to connect and share files with other devices on the same network. Chances are , you don’t use it, and it drains battery because it’s constantly searching for other devices.
Swipe up to bring up the Control Center and turn off AirDrop
10. Push Notifications
Settings > Notification Centre > Switch Show in Notification Centre Off for each app.
These are the notifications you receive after an app update
if your iPhone battery still draining fast after you try all of way, i think you must go Apple customer service around you to find other alternatives.