In the eighties, my sister and I had a box pizza called Momma Bosso's from Aldi (a discount food chain), and it was horrible. Crust didn't set; the sauce tasted like ketchup. It was sort of a soupy mess. That and that old black and white beer that came in cans that just said "Beer" was off the hook crapola.
So what's the worst tasting generic food you've ever had?