In theory the things that would make the "as much money as possible" in such a short amount of time would be some form of gambling. That could be traditional gambling, options, illicit activities (gambling that you escape the law), etc. However, these tend to have a low probability of working out.

So I think we have to define what level of probability you are looking for. Sure thing? Then maybe consulting. Possible with some follow-up work? Then maybe an app, SaaS, etc. High payout but unlikely? Then some type of gambling - options, crypto, traditional gambling, etc.