Are there ingredients I should avoid in a brine? I see good answers to What brine ingredients are effective?, and I am looking to really push the envelope. I realize that there is some debate as to the effectiveness of brine to add flavor to the meat itself, so I'm going to experiment to answer that question for myself. My intention is to brine a big (6 lb) chicken overnight in a 5% salt brine adding tons of flavor to the brine. After brining I think I'm going rinse and dry the chicken and throw it on to my "set-it-and-forget-it" counter-top rotisserie. When the chicken is just about done I'm going to glaze it with a very basic soy-based glaze Mr. Yoshida's.

Some of the ingredients I'm considering, just because I happen to have them on hand, are brown sugar, finely minced preserved lemons, powdered ginger (I'm out of fresh), hot pepper flakes (lots), crushed fresh garlic (lots), any combination of the myriad of whole spices I used in my recent successful pho (star anise, cinnamon stick, cloves, cardamon, fennel), Ras el Hanout, harissa, onion, dry sherry and even fish sauce.

I'm confident that I can play with those ingredients (selectively, of course) and create a brine that tastes good at that point. One of my concerns is the tendency of some ingredients to become more powerful over time. For example, if I use star anise to flavor the brine I will fish it out before I add the chicken. I don't want the final chicken to taste like licorice. Another concern is the possibility that a particular ingredient might cause a chemical change that I don't want. Alcohols and acids come to mind.

Are you aware of any particular ingredients that should be avoided in a brine, or any caveats concerning specific ingredients?
A brine serves two purposes: to make the meat moist and flavorful.

How the moist part works: "Brining makes cooked meat moister by hydrating the cells of its muscle tissue before cooking, via the process of osmosis, and by allowing the cells to hold on to the water while they are cooked, via the process of denaturation." (Wikipedia)

It makes the meat flavorful by acting the same way a marinade does. So you're pretty safe following "standard" marinating rules. Chief among those being that you want to avoid using too much acid or using acid for too long because it might make the meat mushy.

Avoid alcohol as well. "If your marinating anything with alcohol, cook the alcohol off first. Alcohol doesn't tenderize; cooking tenderizes. Alcohol in a marinade in effect cooks the exterior of the meat, preventing the meat from fully absorbing the flavors in the marinade." - Thomas Keller, the French Laundry Cookbook

Remember to use a nonreactive container (no metal) and avoid ingredients like olive oil that solidify when chilled.