The acid which can produce carbon from cane sugar, is:

Concentrated Sulphuric acid

Reason — Concentrated Sulphuric acid acts as a dehydrating agent as it has great affinity for water. It immediately reacts with cane sugar, removes water from it and a black spongy mass of carbon rises up.

C₁₂H₂₂O₁₁ (s) $\xrightarrow{\text{Conc. H}_2\text{SO}_4}$ 12C (s) + 11H₂O