Condiments are great!! Depending on what they are.....
There are ALL kinds of flavored mustard out there: Jalapeno, Yellow, y Brown, etc -- check labels & you can see if they have any cals, etc.... Apple Cider Vinegar is tasty also.
Some pickles (while high in sodium) also can show 0 cals on their labels.....
Otherwise, with ketchup/relish/FF mayo -- measure them & use in moderation.... I doubt that 1 tblsp of ketchup will really harm you.
Tip: With condiments like BBQ sauce, ranch or blue cheese dressings -- Mix in a little water or veggie broth in the bottle to thin it out some. You'll still have the flavor, but won't take as much of a hit with the cals.