re: Root beer as a steak marinade

I don't marinade but I do make a sauce for my steaks from time to time. A good bearnaise sauce is always good. Another I make for filets is:

3-4 shallots chopped
1/2C dry red wine
1/2C balsamic vinegar
2-3TB dark brown sugar
salt and pepper to taste

Using a small dab of butter, saute shallots until aromatic, slightly translucent. Bring heat to high, add vinegar, wine, sugar and reduce by half. Salt and pepper to taste. Strain and serve drizzled over filet.