Gastric juice is secreted from gastric glands after entering the stomach after eating food , it contains HCl pepsinogen. The stomach does not have enzymes like maltase, lactase, amylase, isomaltease , sucrose etc. for digestion of sugars. As a result, sugar is not digested in the stomach. However, saliva of the mouth comes with food , this saliva contains tylenin which somewhat hydrolyzes the sugars in the saliva. And as a result of the expansion of the contraction of the stomach, the food becomes a pulp. No more digestion here. However, the protein is digested.