Izze Sparkling Birch

This is really weird. First off, it makes my tongue numb for some reason. I feel like someone smeared Orajel on the mouth of the bottle. I really don't understand that at all.
It tastes like a very light birch beer. Like the ratio of carbonated water to flavor is really high. It tastes almost herbal tea like.
Really though, someone explain to me the numbing.