Depending on what shortcoming you are complaining about, your choice may vary. Here are a few ideas.
If you want to suggest they may be trying to poison you:
Witches' brew (dictionary.com)
a harmful or threatening mixture; diabolical concoction
a magical broth prepared for an evil purpose, as in black magic.
If you want to bring attention to the quality of the ingredients:
(like) dishwater (Cambridge Dictionaries Online)
describes a drink or liquid that is unpleasant because it contains too much water and has very little flavor
turpentine, paint thinner, or acetone
There are many byproducts of alcohol distillation, called congeners that enhance or undermine the flavor. A poorly distilled alcohol might have more of the most distasteful congeners than your best brands. Acetone is one of these congeners, and it may actually be added to denatured alcohol to make it undrinkable. Paint thinner and turpentine aren't actually congeners, but they say the same thing about the quality of the drink.
Ripple (The Sanford & Son Wiki, for nostalgic reasons)
Ripple was a fortified wine produced by E & J Gallo Winery Low end fortified wine that was popular in the United States, particularly in the 1970s. Possessing a relatively low 11% ABV, it was originally marketed to "casual" drinkers. Due to its low price, it had a reputation as a drink for alcoholics and the destitute.