Drinking soda during eating is way to gain weight?

Yes, but all sugar: If one is truly underweight (based on height, family background, and body type), a Dr. can evaluate for a hormonal, digestive, or other disorder. If no medical cause is found, then one can add weight by eating more calories of nutritious foods, while also doing weight-training to increase muscle. Proteins: egg white, chicken breast, salmon, ... Better fats: olive oil, peanuts, almonds, tofu, ....

Yes: But if you goal is to gain weight - adding all of this sugar to your diet is not a wise way to go about it.