How do I prevent this from happening to my mug?

i recently bought the marvel 60oz. carnage mug, and i had drank a cup of coffee but when i washed it, it had small cracks inside, and stains from the coffee. i tried hand washing it, with soap and cold water, but nothing seemed to work. that's why i wanted to ask here and try to get help because it is my favorite mug, and i wouldn't want to make the same mistake to my other mug.

there's the small cracks and the stains that can be seen.

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