If you have leftover taco meat that's dry, one of the easiest ways to moisten it is with a little water. However, if you want to add some flavor to your meat, you can use a little tomato sauce or salsa. If you're making a dish that calls for cold taco meat, you can stir in the liquid to the meat before adding it to the other ingredients. If you need the meat to be warm, you can warm it in a skillet or the microwave with your desired liquid.