Install a tankless water heater that does not shut off when the tap is closed. Some manufacturers, such as Rinnai, have developed tankless water heaters hold onto the hot water supply for an additional 60 seconds. Although cold water will still arrive when the tank is first opened, it will remain for a minute after it is closed, in case it is turned on again immediately after.
Keep the tap on to ensure there is a steady flow of water. This is an ideal option for activities such as washing the dishes, having a shower or running a bath, where leaving the hot water tap turned on will result in continuous flow of hot water.
Keep the tankless water heater and inlet water filter clean and free of debris. Some water supplies contain high amounts of iron, which could affect the water pressure and cause the hot water to temporarily cut out. You can also remove the showerhead and fixtures and clean those.
Replace the showerhead and fixtures with ones that provide more pressure. The tankless water heater needs to sustain pressure in order to keep the hot water flowing. Some manufacturers require 0.6 gallons per minute in order for the hot water to continue flowing.