Preheat your oven to 325°F (163°C). Prepare a 9-inch springform pan by lining the bottom with parchment paper. Crush Nilla Wafers and mix with granulated sugar and melted unsalted butter. Press into the pan and bake for 10 minutes until golden.
While the crust cools, boil water for the water bath. Beat softened cream cheese until smooth, then mix in mashed ripe bananas and sour cream. Gradually add granulated sugar, banana pudding mix, and vanilla. Beat in eggs until just combined.
Wrap the springform pan in aluminum foil and place it in a larger roasting pan. Pour filling into the crust, then add boiling water to the roasting pan. Bake for 70-80 minutes until the edges are set and the center is jiggly.
After baking, turn off the oven and crack the door to cool the cheesecake for about 1 hour. Transfer to a wire rack to cool completely, then refrigerate for at least 5-6 hours or overnight. Serve with whipped cream, sliced bananas, and Nilla Wafers.