How do you tell if whiskey has gone bad?

Smell the whiskey. This is the most important way to tell if whiskey has gone bad. If it smells off, flat, or strange in any way, it's best to err on the side of caution and throw it out.

Look at the whiskey. If the whiskey is cloudy, murky, or has any sediment, it's likely that it has gone bad.

Taste the whiskey. If the whiskey tastes flat, sour, or bitter, it's likely that it has gone bad.

Take a look at the cork or cap of the bottle. If the cork is moldy or damaged, or if the cap is leaking, the whiskey may have been exposed to air and spoiled.

Check the expiration date. Most whiskeys do not have an expiration date, but they will eventually go bad. A general rule of thumb is that whiskey will last for about 10 years unopened and 2 years once opened.