Child Vomit

My 5 year old woke up this morning vomiting WATER. He’s not feeling so well either, he has no fever. And an hour later he vomits the water again. Can anybody give me any reasons that may cause this? I know no one is doctor but I’m really trying to avoid taking him to the Er because of COVID. I rather take him to his pediatrician Monday. But not if something is really wrong.. thanks