I would highly recommend a whey protein powder, as it is the most commonly used and widely available type. It is also very easy to digest and can be mixed with water or milk for an easy drinkable shake. Here are some of our top picks: 1. Optimum Nutrition Gold Standard Whey - This is one of the most popular protein powders on the market, offering a great balance of quality ingredients at a reasonable price point. It’s also available in many different flavors to suit your son’s preferences. 2. MusclePharm Combat Protein Powder - This is another great option that offers a high-quality blend of whey protein, egg albumen, and soy isolate for added aminos. It’s also available in several delicious flavors like chocolate and vanilla bean. 3. Dymatize ISO 100 Protein Powder - If your son is looking to add more plant-based proteins into his diet, this could be a great option. It features a blend of whey protein isolate, pea protein isolate, and hemp protein for added variety and nutrition. I hope this helps! Let me know if you have any other questions or if there’s anything else I can assist with.