Thanks @missy, @rambo, and @lyxzen, for picking such a short and sweet one!
My favorite drink of all time has got to be the Green River. (Photo not mine.)
Green River soda was first introduced in 1919, by the Schoenhofen Edelweiss Brewing Company of Chicago. Prior to 1920, the brewery produced the popular Edleweiss beer. Schoenhofen began manufacturing Green River and other soft drinks in order to survive the Prohibition Era.
It's sold in Chicago at Benny's beverage depot, and a few other places. Sometimes Kroger will have it in store, or Walmart online. If you're in Indiana and come across a Schoops Diner, have a green river fountain or milkshake, they are divine.
I have such an attachment to these because the sweet shop where I grew up had them on fountain and my mom and Grams would take me there to get them. It closed down when I was in first or second grade, but I can still remember. Whenever I find them I always stock up!