There isn't a definitive answer to this question as different people react differently to different types of fiber. However, soluble fiber is generally considered to be the best type of fiber for promoting regularity and improving stool quality. Additionally, insoluble fiber can also be beneficial for making you poop by adding bulk and helping food move through your digestive system more quickly. Some good sources of soluble fiber include oats, flaxseeds, chia seeds, nuts, and beans. Insoluble fiber can be found in foods like wheat bran, vegetables, and whole grains.