Quick answer
CAN bus carries data as a small voltage difference between two wires, called CAN high and CAN low. Twisting the pair keeps the two conductors close together along their whole length, so any external electrical noise couples into both wires almost equally. The receiver looks only at the difference between them, so most of that noise cancels out.
This is why vehicle harnesses use a twisted pair for CAN rather than two loose wires. Pair length, lay and routing away from ignition and high-current cables all affect reliability. The APAR range includes CAN bus cable of the UTP-A type to SAE J1939/15, listed on the automotive and EV harness page.