Then you have probably misjudged the risk. When promising costly things (such as reading a thick boring book) if a condition X is satisfied, you should at least make sure that X is specific enough to be verified easily and unambiguously. X = "a religious apologist presents enough evidence" is too vague for that. More generally, never promise anything to religious apologists for their ability to construct arguments. Their debating strategy is optimised to exploit such promises. Even if you later realised that they weren't exactly fair and you weren't obliged to pay your part of the deal, your trustworthiness and status are nevertheless damaged by apparent defection.