If your car is fine all day but dead in the morning, something is drawing current with the key off. Common culprits: a glove box light stuck on, a dome light not switching off, an aftermarket alarm or stereo wired wrong, a phone charger left in a 12V port.
Quick test: pull the battery negative cable for a night. If the battery is full the next morning, you have a parasitic draw. If it's still flat, the battery itself is shot.
We diagnose parasitic draws on scene at our $249 / hour rate — multimeter on the negative cable to isolate the circuit pulling current. Most diagnostics finish inside the 1-hour minimum.