What's the best way to track cash spending that doesn't show up in my bank app?

Cash is the blind spot in app-based tracking because withdrawals show up as a lump sum, not as the coffee, tips, and small buys they become. The simplest fix is to reduce cash use for anything you want to track, shifting to a debit or credit card that categorizes automatically. If you prefer cash for budgeting discipline, log spends immediately in a notes app or a small notebook, or snap a photo of receipts and total them weekly. Alternatively, treat a fixed cash withdrawal as a single spending allowance, once it is gone, you are done, so you do not need to track each item. The goal is either eliminating the blind spot or capping it so it cannot silently wreck your plan.