Dietary Fiber with Crunchy Texture
I want to explain few things about dietary fiber.

Soluble fiber is not digested in the small intestine but it can be fermented in the large intestine by normal intestinal bacteria into nutrients (which are absorbed) and gases. Soluble fiber can have 1-3 Cal/g (sugar, starch and other digestible carbohydrates have 4 Cal/g) and can cause bloating and gas. For exact calorie value of the exact fiber, you need to check the Nutrition Facts labels. Or you can check in MyFitnessPal, which says that, for example, 1 tsp of glucomannan has 10 Calories.

Examples of soluble fiber (naturally present or added to foods):


Fructooligosaccharides (FOS), inulin, galacto-oligosaccharides (GOS), isomalto-oligosaccharides (IMO), lactosucrose, mannan-oligosaccharides (MOS)
Beta-glucan (in whole barley and oats)
Pectin (in apples, bananas...)
Gums: acacia (arabic), beta-mannan, carob (locust bean), fenugreek, glucomannan (konjac), karaya, tragacanth, guar, tara gum
Resistant starches (in potatoes)
Algae and seaweeds agar, alginate, carrageenan
Other: arabynoxylan 


From the digestion viewpoint, sugar alcohols (isomalt, maltitol, mannitol, sorbitol, xylitol) are similar to soluble fiber; they have ~2 Cal/g, except from erythritol, which has close to zero calories. 

Insoluble fiber is not digested in the small intestine and not fermented in the large intestine, so it has practically zero calories and does not cause gas.

Examples of insoluble fiber:


Cellulose (in whole grains, in cabbage family of vegetables, in fruit skins...), hemicellulose and methylcellulose (as an added thickener)
Lignin (in wheat bran, flaxseed...)


Many of these fibers are available in markets. Before buying, find the info about "relative sweetness."

Here's the source with links to all individual fibers.

Here's an one page comprehensive article about Texture modifying agents, such as gelatin, corn starch, pectin, guar gum, methylcellulose, etc.