Lightly spray a 6 cm-deep x 20 cm x 20 cm square baking dish, and line base and sides with baking paper.
Place peanut butter and honey in a small saucepan and heat until melted. Set aside to cool.
Place sultanas, coconut, Weet-Bix, cacao, water and cooled peanut butter and honey in a food processor and blend until mixture is well combined and smooth.
Press the mixture into the baking tin and refrigerate for 2 hours.
Slice into 8 pieces.
If freezing, once sliced into portions place in individual freezer bags or large container.