If you know it is the tank that is leaking and not some line, I can just about promise you that you will have to remove the tank and replace it. Most of these tanks are plastic, so most glues will not stick to them. You might be able to plastic weld the tank, but even then, if the tank cracked, it is likely the plastic has turned brittle, so the repair will not likely hold up long term.
I had a similar issue and welded the tank. Shortly there after, it began to leak in a new spot. It was an ongoing problem till I finally gave up and replaced the tank. There is a reason the tank failed to begin with. If you have not addressed the root cause of why it failed, then you are not fixing anything.
IRV2