In a medium bowl, combine one can of sweetened condensed milk, one cup of cold water, and one package of instant vanilla pudding mix. Whisk until smooth.

While the pudding thickens, pour in two cups of heavy cream and whip on medium speed until soft peaks form, adding sugar and vanilla if desired.

Fold the pudding mixture into the whipped cream gently until combined.

Layer Nilla wafers at the bottom of a trifle dish, followed by sliced ripe bananas, and then a layer of the pudding mixture.

Continue layering with Nilla wafers, banana slices, and pudding until all ingredients are used, finishing with pudding on top.

Cover and refrigerate for at least four hours before serving.