If it ends in "ose", avoid it!
I'm diabetic and I agree with Jigz: if it ends in "ose", avoid it (except for sucralose, which is Splenda). Some diabetics are counseled to avoid all "ose" sugars, no matter how slow or fast the scientist say it's absorbed. Better not to use it- that goes for honey, too.
I use Heinz Low Carb ketchup. It's a bit sweeter than the usual product (whichI think is plenty sweet) but it could be a good base to start with. It's sweetened with sucralose and has the tang and tomato flavor you'd want for a tomato-based sauce. Now if you're going for one of the vinegar/mustard based sauces, you wouldn't have a very sweet sauce at all.