Water has a specific heat capacity of about 4.2 Kilojoules per kilogram per degree Kelvin, so it would take about 6 Kilowatt Hours of electricity to heat 100 Litres of water from 15 degrees centigrade to 65 degrees centigrade. As a standard immersion heater is 3KW, so it would take 2 hours to heat 100 Litres of water.
Drinking a large amount of carbonated drinks at bedtime can also cause hiccups, as the air in these drinks can distend the stomach. Consuming a large amount of alcohol before going to bed is another possible cause of hiccups during sleep. The excessive amount of alcohol can cause the stomach to distend.
What actually causes the hiccup is difficult to say â in most instances, there is no obvious cause. Attacks of the hiccups seem to be associated with a few different things: eating or drinking too fast; being nervous or excited; and, having irritation in the stomach and/or throat.