Never put 100% sulphuric acid into any battery.
Normally batteries once filled should only need distilled water.
If the thing has been spilled and left for long it will likely be sulphated beyond recovery.
If you want to try and save it, I would fill it with water with a spoonfull of EDTA added and try to charge it. It will take a long time but it may respond. It will require several charge/ discharge cycles.
When it shows signs of working, empty it out and refill with diluted acid at about 1.25 sg. Fully charge it until the sg is constant then adjust the sg for standard value ( compare with the others) likely about 1.25 to 1.28 depending on duty it was intended for.
Flux