Heat oil:

Pour oil to a depth of 2 inches into a deep pan set over medium-high heat. As an alternative, preheat oil in an electric fondue pot or deep fryer to 375°F (190°C).

Cut biscuits:

Unseal the biscuit tube and slice each biscuit into 4 equal portions.

Mix cinnamon sugar:

Combine the sugar and cinnamon in a small bowl, mixing thoroughly.

Test oil temperature:

To test oil temperature, insert a wooden spoon: steady bubbles indicate readiness; violent bubbling means the oil is too hot.

Fry doughnut holes:

Once oil is hot enough, fry 6-8 doughnut holes per batch, avoiding overcrowding.

Flip and cook:

Cook each batch until the underside is golden brown, then flip and cook the other side until both are golden, about 1-2 minutes in total.

Coat in cinnamon sugar:

Transfer finished doughnut holes to a plate lined with paper towels. Blot away extra oil, then immediately coat them in the cinnamon-sugar mixture.

Serve immediately:

Continue with remaining batches. Serve right away.