Probars DO have sweeteners. Take a look at Art's Original in the first 3 ingredients are 2 sugars:
Ingredients: Natural unsalted peanut butter (peanuts), brown rice syrup, barley malt syrup, fruit and nut mix (raisins, sunflower seeds, juice sweetened papaya, juice sweetened pineapple, dates, cashews, unsweetened coconut, pumpkin seeds, brazil nuts), granola (rolled oats, raisins) corn flakes (corn, flour, mixed fruit juice concentrate), organic rye, crisp brown rice (brown rice and malted barley flour), organic evaporated cane juice, grape concentrate, expeller pressed canola oil, brown rice syrup, flaxseeds, hemp seeds, almonds, apples, oat bran, organic oat syrup solids, sea salt, organic molasses, rice bran extract, epasote, prune powder, cardamom, fennel, fenugreek, nutmeg, natural orange oil, carob chips (whole grain malted barley and corn, palm oil, carob powder, soy lecithin), almonds, raisins, dates, oranic sunflower seeds, organic unsweetened coconut, organic flax seeds, organic brown sesame seeds.
Some flavors contain ariabic gum, while natural, is a binder.
I am not picking on the bars, my husband likes them, but rather that yes, they are full of not-so-hidden sugar!