Lactate/Lactic acid is a byproduct of broken down glucose, but also temporarily picks up the slack in energy when the body can’t supply enough oxygen to breakdown glucose for energy requirements. Lactic acid is used in the mitochondria of cells and keeps the heart pumping during these intense phases of exercise where the oxygen/glucose can’t do the job...again as lactic acid is temporarily being used as fuel it would follow glucose builds up as the body can’t break it down fast enough and is now using an alternate fuel source.
Creatine as I understand it isn’t a fuel/energy directly, but does facilitate recycling of energy. Moreover, as ATP (energy) is produced in the mitochondria and used by the cell it is converted into ADP, but the body/muscles will use creatine to recycle ADP back into ATP. On its own though I don’t think creatine is fuel/converted into ATP at any point like glucose/ketones.