ANSWER:
If it was a gift for a person in exchange of something he had done or tried to do, this is permissible as in the case I challenge someone that if he climbed that mountain, I will give him money for that but I am challenging him as I don’t believe that he can!
But if this money was for no work as if I say that this team will win and he says that the other team will win, and i say if your team wins, i will give you this or that, this is not permissible as he didn’t work for it and it is extravagance from my part.