Can you gain Temporary Hit Points when unconscious?

Question

If you are at 0HP with max HP of 0, is there any Temporary Hit Point generation mechanic that works? If it does, will you become conscious?

Answer 1

No - Temp HP will not allow you to become conscious at 0 HP

There is no rule that prevents an unconscious creature from gaining temporary hit points. Thus, any method that normally allows one to gain temporary hit points should still work when a creature is unconscious. For example, someone could cast Enhance Ability (Bear's Endurance) on the unconscious creature.

However, they will not allow you to become conscious again if you do gain them:

If you have 0 hit points, receiving temporary hit points doesn't restore you to consciousness or stabilize you. They can still absorb damage directed at you while you're in that state, but only true healing can save you. (PHB)

Answer 2

Yes - but you remain on 0 hit points, are still unconscious and must continue to make death saving throws if you have not stabilised.

This is explicitly stated in the rules: Temporary hit points (PHB p. 198):

• If you have 0 hit points, receiving temporary hit points doesn't restore you to consciousness or stabilize you. They can still absorb damage directed at you while you're in that state, but only true healing can save you.