For the orange sugar:
1) Place zest, sugar and cinnamon in a paper bag and shake to combine.
For the donut holes:
Place oil in a deep pan until it comes about halfway up the side of the pan. Heat oil to 180 degrees C.
2) Slice biscuit dough in quarters and roll into balls to form 24 donut holes. Working in batches, place donut holes in hot oil and fry until golden, about 6 to 8 minutes. Transfer the hot donuts to the paper bag and shake to coat with orange sugar. Serve immediately.