My dad bg was 103 before bed 14 hours later no food it was 153 only thing he had was coffee before checking how come it spiked like that?

Metabolism: Food is still being digested as we sleep and can cause blood sugar to increase into the morning hours.

Liver produces sugar: The liver breaks down glycogen to glucose overnight when one is asleep, in order to feed the body (when not eating). In people with type 2 diabetes, this liver production of glucose is exaggerated, and often times leads to elevated fasting morning glucose levels, which may actually be higher than the readings from the nights before. There are medications that can help to control this.