Either something is draining the power - or the battery is at the end of its useful life.
Either a short to power or a bad fan switch.
Defective alternator, loose alternator drive belt, dead cell in battery, or something is on pulling power from the battery.
Then either something is on draining the battery or the battery has a dead cell draining all the rest and must be replaced.
Something is on an pulling power from the battery. Check the lights in the glove box, trunk, under-hood, interior. Check for a stuck relay. Power windows, power seat, power door lock, fuel pump relay, etc.
Dead cell in the battery, or something is on pulling power from the battery. Any light on the vehicle or any relay that is stuck. I am assuming you have checked the alternator and it is good.
It shouldn't be draining that fast unless you have a light on or something. The battery might be bad. For longer periods of inactivity you can disconnect the battery because the computer and radio draw small amounts of power even when turned off.
A short will not drain the battery it will blow a fuse. It may be the battery has a dead cell, or some light is on draining the battery. It can also be a stuck relay.
If the battery is brand-new and I would suspect either the alternator is defective or you have a lightbulb somewhere on the vehicle that is pulling power from the battery. It can also be a relay that is stuck.
Something is draining the battery. Check all lights. Glove box, trunk, etc. Also check the power window switch.
Something is on draining your battery overnight. Any light or any relay. It can also be your battery has a dead cell draining it overnight.
The coin if conductive could short out the battery draining it of all its power. If the coin is no conductive it could act as an insulator breaking the flow of electricity.