Most exams do not pay any travel or daily allowance — candidates bear their own travel costs.
Some recruitments, like the railways, reimburse sleeper-class train fare to SC/ST candidates for certain stages.
Where reimbursement exists, you must keep your tickets and claim it at the venue as instructed.
The notification or call letter always states whether any travel allowance is admissible.
If it is not mentioned, assume no reimbursement is available.