This article explains two ways to turn Bluetooth on or off on an iPhone or iPad running iOS 7 or later.
2 Ways to Turn Bluetooth On or Off on iPhone
The Control Center method is a quick solution since you don't have to dig into the Settings app. However, this method only disables Bluetooth until 5 a.m. local time the next day.
With this method, the Apple Watch, Apple Pencil, AirPlay and AirDrop services will work, even though they use Bluetooth to communicate.
Open the Control Center on your iOS device.
