Identify what you need banana for: binding/moisture (baking) vs creaminess (smoothies) vs sweetness (sauces).
Choose the closest substitute from the list and use the stated ratio to replace mashed banana.
Adjust texture: if your batter seems thick, thin with 1–2 teaspoons water or milk; if it’s runny, add 1–2 teaspoons oats or flour.
Adjust flavor: taste after mixing and add a pinch of salt to balance sweetness or a tiny squeeze of lemon if the puree tastes flat.
Let baked goods rest 5–10 minutes so the substitute fully hydrates and the crumb sets.