A voice that sounds like it is not a native English speaker or a voice that actually speaks another language? In either case a foreign voice can represent a solution for both.
There are two possibilities when you need to use a foreign voice. One is a when the message, ad or the text needs to be in English language, but needs to sound as if it is spoken by somebody who is non-native English language speaker. The other is that the text has to be actually in another foreign language. In this instance, the voice has to be as specific, i.e. localized for the intended audience in that language.
When the audience needs to hear a foreign voice that is actually speaking in English, the audience is either originally from a specific country, i.e. Germany, France or Russia, for example. At the same time, the audience that does not speak that specific language needs to hear the same message. It could be that it is an ad for a product originating from a specific country, or that the impression has to be made for an English speaking audience that voice originates from that country. On the other hand, a foreign voice in another language is geared to an audience speaking that particular language and follows all the rules of localization for such a country.
Whether the foreign voice is speaking as a foreigner that is delivering a text in English or in another language, the vocal presenter has to be fully versed with all the nuances of a specific language, with its accents and slang expressions. Preferably, it should be a native speaker of that language.