It might be that you need to replace the spark plug.
It may be that the charging system is not working. Charge the battery and drive the vehicle to your local auto parts store and they will test the charging system for you at no cost. It may be the alternator is At Fault.
Is there power to the starter "S" terminal? What car?
Something is on pulling power from the battery. Can be any light on the car or a stuck relay.
The battery just isn't holding a charge. Time for a new one. Batteries can die suddenly like this.
You may still be able to charge it up.
The car may need a new alternator.
I had the same problem with my car this resulted in me going to a shop and having to get a new alltenator.
Get a new battery, mine was doing the same thing. No matter how charged it is, youll still need a new one.
You can get a new battery, you can jump start the car with jumper cables and another car with a charged battery. You can also put a battery charger on your battery to give it a charge.
The the alternator is defective.
Go get a new battery using another car. Or get the dead car jump started using another vehicle. There are companies that have mobile battery services that will come right to your home or wherever the car is located and replace the battery.
A new battery or one that tested good is in the vehicle and the car is still losing power. the alternator is what charges the battery while the vehicle is operating.
Disconnect negative cable first from old battery and connect it last when installing new battery.