Some people train really early in the morning at 5 a.m. If that's the case, you may not feel like eating, and I completely understand. That's why they make things like essential amino acids that can help preserve muscle mass and give you a little boost during your workout. You can learn more about amino acids in this blog.
It's very important to have something in your system before you work out to allow your body to tap into some fuel source. Your body will tap into fat if you don't have anything in your system, but it can also tap into muscle tissue, which is why you need to eat something.