They have the same meanings,but the phrase"Don't you dare"means more fiercely,it's just a way to accentuate and strengthen your expression and emotions. So that's the difference between them.Hope this can satisfy ya.

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'don't dare ' is more of an order or command. 'don't you dare' is lighter in meaning and could be slightly used in an sarcastic tone.

No difference.

Don't you dare is a warning to someone not to do something and it is used, for example, when a parent is giving a warning to a child. For example, "Don't you dare throw water on your sister." There's a condescending tone to it which is why when one adult says it to another (unless jokingly), it might not be accepted well. Don't dare is telling someone not to risk doing something. It's another way of saying "If I were you I wouldn't do (something)."