Disable Auto App Updates
Although the automatic app updates are a wonderful addition that saves you quite a bit of time, it will drain your iPhone battery. Instead of having your apps automatically update when there is an update available, you can turn this off and set it to update only when you want to manually.
Go to Settings > iTunes & App Store, then disable Automatic Downloads for apps listed there. At the very least, toggle off the “Use Cellular Data” option so that apps only auto-update when you’re connected to Wi-Fi.