How come sometimes when you wake up your throat hurts really bad?

Several Reasons: One possibility is post nasal drip. While you are laying down, mucus from your nose drains down into your throat (your nose & throat are all connected in the back). This can cause a sore throat when you wake up. The mucus could be from an infection or allergies. Another possibility is dryness. At night your throat can dry out, esp. If you breathe through your mouth. See dr if worsens or concerned.

Multiple causes: If you're an otherwise healthy young adult, the first thoughts that come to mind are postnasal drip (common with allergies as the mucus your body makes drips down your throat at night) and acid reflux (especially if you wake up with a sour taste in your mouth). You can try sinus rinses and drinking more water to dilute mucus. Dryness from snoring can also cause your throat to hurt upon wakening.

Many reasons: If you're an otherwise healthy young adult, the first thoughts that come to mind are postnasal drip (common with allergies as the mucus your body makes drips down your throat at night) and acid reflux (especially if you wake up with a sour taste in your mouth). You can try sinus rinses and drinking more water to dilute mucus. Dryness from snoring can also cause your throat to hurt upon wakening.

Vocal trauma: You are probably overusing your voice and not resting it or drinking enough fluids. Cigarette smoke, both active & 2nd can harm it. Postnasal drainage can irritate your throat as you sleep as can acid reflux.