"What was the absolute worst swill you ever imbibed? And, what made it so terrible? Awful flavor? No flavor?"

The drugstore chain Walgreen once released their own beer called 'Big Flats'. It hardly had a taste and what little taste it did have was bad. I can describe it like this:

Take a can of Busch beer. Dump half of the can out and fill it with tap water. The beer is now a Natural Light. Take the can of Natural Light and dump half the can out. Refill half the can with water. This is now watered down Natural Light. Dump out half of the can of watered down Natural Light. Urinate into the can. Now it is a can of Big Flats.