its likely acting like a sponge for moisture and off-gassing its nasty formalgihyde (spelling?) resin/glues and will continue to do so no matter what.

You *MIGHT* be able to seal the smells with a shellac sealer like original BIN.

Here is the rub: The underside, back (against the wall) edges, drawer backs, etc. would still be unsealed – yet able to absorb the ambient moisture produced in the bathroom during normal bathing/showering activities.

A bathroom exaust fan run during any water activites, and for sufficient time thereafter would be a must.

Of course if the “sweet” smell comes from something else (like a spill or other nasty odor) which was sucked up by the vanity via the FLOOR contact point – nothing is going to solve the problem other than replacing the vanity.

Something as simple as condensation from the toilet carried along a tiled floor to the vanity base can be responsible for this – of course other liquids/combinations could be responsible as well.

One man’s sweet is another man’s stink.