I just bought myself a used car and one day i started it and the battery was dead so i started charging it but amps weren’t showing any progress and it was smelling like sulfur acid and when opening a cap the "water"in it was boiling. what does this mean? does the battery need to be replaced with a new one?
Ummmm, yeah!
And, I hope you disconnected the charger, like, really quick!
You’re flirting with disaster.
A boiling battery might just decide to explode while your face is looking down into a battery cell.
This could ruin your whole day.
What car did you buy? How old is the battery? What are you using to charge the battery?
We need some information.
yeah i knew i had to buy another one but i just wanted to be sure tomorrow and heading out to buy it 
i have a toyota ECHO 2001 and i dont know how old the battery is (it has no sticker no nothing) which is why i still had some hope…
but ive been doing some research and apparently the fact that it kinda boiled is a pretty clear sign that this battery is ready to be disposed hehe
my day is kinda ruined also jeje so you were right about that too
thank you for the help hehe and im even kinda ashamed cause now it seems silly that i asked that :S
A few bubbles while charging a full or nearly full battery is normal.
Vigorous outgassing that looks like boiling is definitely abnormal.
When I fully charge a car battery I take the caps off.
One thing I watch for (at the end of the charge) is an equal amount of bubbling in each cell.
That means the cells are still well matched.
Outgassing increases rapidly when charge voltage rises above ~14.5V, as some fast, “boost” or non-automatic chargers will allow.
Automotive and deep-discharge “wet” batteries can benefit from an occasional “equalizing” charge at 16V (8V for a 6V battery).
This is done for an hour or so and after the battery has been fully charged at a lower voltage.
It sounds like one or more cells of the OP’s battery were shorted. Since the battery can never reach full voltage, the remaining cells will be overcharged in the attempt. He’s lucky it didn’t explode in his face.
Time for a new battery…GOOD THING you werent SMOKING at the time of the batt exam. BOOM!..not fun or funny…those vapors are FLAMABLE…
I hope you were wearing safety glasses. Never mess with a battery without them!
The old battery most likely had a shorted cell which will cause the other cells to be overcharged due to the higher voltage placed across them from the charger.