I think I’ve had Faygo Rock & Rye, but I don’t remember what I thought of it. I have at least been around people drinking it. I going nuts trying to remember which Grateful Dead song goes

Hello baby, I’m gone, goodbye
Half a cup of rock and rye

It’s Mississippi Half-Step Uptown Toodeloo. Also, I always heard it as “have a cup,” not “half a cup.”
Also, the Grateful Dead were presumably singing about rye whiskey and rock candy, not Faygo.