Bathroom sink clogs are commonly caused by hair, toothpaste, and soap buildup near the stopper or trap. Start there before reaching for corrosive chemicals.
Remove and clean the stopper
Many clogs are caught on the stopper mechanism. Remove accessible hair and debris with gloves, then test drainage again.
Use a small cup plunger if available
Cover the overflow opening with a wet cloth, leave a little water in the basin, and plunge firmly. This often works better than pouring random chemicals down the drain.
The trap is the next logical place
If you know how to remove it and have safe access, place a bucket underneath before loosening the trap. Do not open it if chemical drain cleaner is present because caustic liquid may spill out.
A recurring clog may be farther downstream
If several fixtures drain slowly or the sink reclogs after the stopper and trap are clean, the blockage may be farther down the branch line or venting system and needs broader diagnosis.