If you don't know who Dr. Bernstein is, he is a diabetes doctor who is pretty famous around these parts. He says certain sweeteners are fine to use and won't spike bg while others can. He listed some of those that can, so I typed up the list and keep it in my purse. Before I buy a new product, even if it says sugar free or no sugar added, I check the ingredients agains Dr. Bernstein's list, and if one of the ingredients is in there, I don't buy it. The list might also be helpful to you.
Most of the diet drinks I have looked at use aspertame as the sweetener, and Dr. Bernstein does approve aspertame.
carob
corn syrup
dextrin
dextrose
dulcitol
fructose
glucose
honey
lactose
levulose
maltodextrin
maltose
mannitol
mannose
molasses
saccharose
sorbitol
sorghum
treacle
turbinado
xylitol
xylose