Hi Jake!

I'd say it depends on what low carb plan you're following, but fruit juices of any kind would be pretty much out of the question. Juicing fruits only concentrates the natural sugars in the fruit and so an 8 oz. glass of orange juice could wind up being about the same as eating 4 or 5 oranges at one time.
A little tomato sauce would be okay as long as you count the carbs in your daily allowance. You could also try soy sauce or mayonnaise mixed with some seasonings (or even just by itself!)
Whole grain breads? Hard to say without knowing how many daily carbs you are allowing yourself. Generally, the majority of your carbs should come from low carb veggies and on most low carb plans, grains of any kind are not added back in until you in pre-maintainance or maintainance.
Fast foods? Most fast food places offer salads but check the dressing for the carb count; generally ranch or bleu cheese dressings are the lowest. You can always order a burger and toss the bun or a grilled chicken sandwich and, again, toss the bun. Stay away from anything breaded or battered.
Alcohol is a YMMV (your mileage may vary) thing, but be aware that your body will use alcohol for fuel in preference to fat so if you are drinking, it could slow down your weight loss. Many people report a much lower tolerance to liquor when they are low carbing also, so always follow up any drink with plenty of water or you would find yourself waking up with a doozie of a hangover the next morning. Hard liquor doesn't have any carbs, but use a sugar-free mixer such as Diet Coke instead of regular. You wouldn't believe how many grams of carb are in a single can of regular Coke and they're all in the form of sugar.
If you haven't settled on a low carb plan yet, I'd encourage you to check the link on the right side of the page titled "which low carb plan is right for me". There are quite a few low carb plans with varying levels of carb. It's always easier if you have a plan, especially when you are just starting out, instead of just winging it on your own. Once you pick a plan that you think fits your lifestyle and tastes in general, please make sure to get the book and read it thoroughly; they contain much information and a lot of tips that make the switch to low carbing that much easier. I wish you good success!