When someone sanitises something, they make it clean and free from germs.
Sanitising is usually a good thing because it helps keep things healthy and safe.
Examples:
She sanitises her hands before eating.
The restaurant sanitises the tables after each customer.
He sanitises the toys to keep them clean.
The nurse sanitises the medical equipment to keep it safe.
He sanitises the entire house from top to bottom.
The cleaning crew sanitises the school every night.