It can normally take about ten hours for a dog’s digestive system to completely process what he has eaten. So it’s not unusual for a dog to vomit what he may have eaten the previous evening.
Dogs can vomit for a lot of different reasons and as long as the vomiting does not keep happening, it’s likely just an isolated incident and no cause for concern, especially if he continues to eat and drink normally. If the vomiting becomes more frequent, it could be a sign of something serious and you should have your beloved friend examined by a veterinarian.