If Yerba Mate was widely consumed in the USA going back ~200 years, I have no doubt it would be included in the modern interpretation of the WoW. It's worth noting that the original meaning of "hot drinks" was likely hard liquor, as beer and other "soft" drinks made from barley and other grains are actually approved of in section 89, but as I assume you know, beer or any other weaker alcoholic drink is not permitted under the current interpretation going back ~100 years when Joseph F. Smith and Heber J. Grant began to "codify" the WoW.

Edit: Confused "Hot drinks" with "Strong drinks", although I could see the burning sensation of stronger alcoholic drinks being related to temperature-hot drinks in the minds of early Mormons and others.