Buy from the health food store or supermarket. Look for non-genetically modified soy milk and check the ingredients for additives. Avoid overly sweetened brands with other additives. Some varieties have kombu added which is good as it improves the digestibility of the product. Added barley malt is a better sweetener than cane sugar.
Once opened store in the fridge for up to 6 days.
Tips & Tricks:
If there is a suspicion of lactose intolerance try soy milk instead. Vitasoy processes are specially designed to retain the essential nutrients found in the soy bean and the unique rich colour, typical of quality soymilk. When you are buying soy milk make sure you select a brand that stipulates it is made using whole soy beans. Some brands of soy milk use highly refined soy protein isolates, which are extracted using chemicals and alcohol from whole soy beans. Always check the ingredient list of the soymilk you drink to make sure it includes whole soy beans.
Heat soy milk gently and avoid overheating as it will separate.