Cats can drink soy milk. Soy milk is rich in plant protein, as well as vitamins, calcium, iron, and other nutrients, which can effectively provide the nutrition needed by cats. However, cats absorb plant-based protein relatively poorly, so it's important to feed them soy milk in moderation to prevent indigestion, vomiting, or diarrhea. If your cat shows any adverse reactions during feeding, stop feeding immediately. It's generally recommended to use goat milk or purified water as your cat's primary beverage. 
Precautions for giving soy milk to cats:
1. It is recommended to give cats unsweetened soy milk. While added sugar may suit human tastes, cats cannot digest the sugar, which is detrimental to their health.
2. Feed small amounts only. Cats are carnivores and require a high intake of animal protein, but absorb less plant protein. Therefore, it is not recommended to feed cats large amounts of soy milk to avoid harming their health.
3. Cats should primarily drink goat milk or purified water. They need to consume enough water to replenish their body's nutrients.
