Sore throat - audition - ASAP?

1) Get one of those sprays that numbs the throat. Bring it with you and use it before the audition.

2) Bring some hot water with just a little lemon juice squeezed into it (no more than you'd use for a cup of tea). Sip it like tea before the audition to soothe the throat and thin out some of that "gunk."

3) Consider ways to alter how you act the scene to compensate for a possibly weaker voice. If you were playing a villain, for example and originally planning to play it loud and aggressive, consider changing the presentation to low-key and conniving.

paracetamol?