This bacon is a little bitter.
This medicine is very bitter, so brace yourself!
Be careful not to let the caramel burn or it will taste bitter.
The kanji for 苦 means suffer. This word, however, is quite different. It means bitter tasting. Just think of ways you can suffer, though. Then, think of putting the most bitter thing in the world in your mouth. You feel sick, your mouth gets all weird, and you try to spit it out but the bitterness remains. Bitter tasting things are super gross.
Like the word meaning, the reading is an exception as well. You can remember it by thinking:
The taste is so bitter that you fall to your knees really, really hard. Luckily, you were wearing your knee guards (にが). Feel the relief that you were wearing them. Ack, no relief now. It's still bitter in your mouth.