Trending @Capgemini; Need suggestion

I have got an offer letter from XYZ company, Now i have cleared another company ABC. And told I have got XX offer from XYZ. Now ABC is asking to share the offer letter for justification. What should I do now? Should I share the offer letter from XZY to ABC? If I don’t share then ABC will drop the candidature! Please help on this situation. It is a clearly unethical situation I understand! But still need more suggestions and opinion.