Choose milk or water based on your goal. Mixing with water keeps calories lower and may feel lighter on digestion, which can be helpful for fat-loss plans or sensitive stomachs. Mixing with milk increases total calories and protein, and often improves taste and satiety—useful for weight gain or for people who need a more filling option. If you are lactose intolerant, consider lactose-free milk or plant milks. Keep in mind plant milks vary: soy typically provides more protein than almond or oat. Texture and preference also matter for consistency. There is no single correct option; the correct choice is the one that fits your daily calorie and protein plan and does not create digestive issues. Label awareness is key because the “same scoop” can become a very different meal depending on what you mix it with.