Actually, cats can drink Christmas tree water and it's not harmful to them. The water from your Christmas tree can actually be a good source of hydration for cats, especially if they are dehydrated. However, it's important to keep in mind that the water from the tree may contain preservatives, which can cause stomach upset in some cats. Additionally, it's important to make sure that the water is fresh and free of bacteria. So, if you have a cat, it's best to provide them with fresh water daily and keep the tree water away from them.