When sourcing protein drinks, you must prioritize the protein source (Whey, Casein, Soy, or Pea) and its bioavailability. Ensure the protein content per serving aligns with your target market (typically 20g-30g). It is critical to verify the Amino Acid Profile, specifically the BCAA (Branched-Chain Amino Acids) content, to ensure muscle recovery efficacy. Additionally, check for solubility and stability to prevent sedimentation during the shelf life, and confirm that sweeteners and additives used are food-grade and clearly labeled.