Multiple income streams is the best starting point imo if you don't know what you want to double down on. Getting $100k itself is not an easy task, let alone trying to get $100k off of a single thing. It's easier (and more pragmatic) to get to $100k by getting $5k on product A in YRR, $20k on product B etc... These things will eventually add up and need to be easily maintainable projects (as opposed to timesink projects). I wouldn't recommend writing a super complex app consisting of millions of lines of code for example that requires a lot of support towards your customers; instead, consider writing an e-book and selling it for $10-30 a pop. Or a SaaS that nets you $10 MRR per customer.
Another upside imo of this approach is that you can discern at a later stage which one of your projects is most successful and has the most chance of getting you to $100k YRR, on its own. This will allow you to decide if you want to double down on it or not.
Also, consider building things someone wants: I know, I know, easier said than done, but it's often a good place to start at what you'd like yourself. In a worst case scenario, you'll at least have 1 customer (yourself) ;-)
Another upside imo of this approach is that you can discern at a later stage which one of your projects is most successful and has the most chance of getting you to $100k YRR, on its own. This will allow you to decide if you want to double down on it or not.
Also, consider building things someone wants: I know, I know, easier said than done, but it's often a good place to start at what you'd like yourself. In a worst case scenario, you'll at least have 1 customer (yourself) ;-)