I use GMSMapView from Google Maps iOS SDK in my application. I can change app language in settings page. How to change language on map in runtime?
As answered in Using the Google Maps APIs - How can I get the Google Maps APIs to display in a language other than English?:
By default the API will attempt to load the most appropriate language based on the users location or browser settings. Some APIs allow you to explicitly set a language when you make a request.
From there, you may add language
parameter in your HTTPS request in some Google Maps APIs. However, for some APIs that doesn't allow this, you have to first determine the current location with the use of Core Location Framework as suggested in this SO post - iphone default map app open with different language.