Run the garbage disposal and water at the same time to clear out any debris or potential liquids that may get smelly over time like milk.
Turn off water and garbage disposal.
Squeeze half lemon into the disposal and cut rind into pieces and place into the disposal.
Turn on disposal for a second or two. This ensures the lemon is spread evenly inside the garbage disposal. The rinds will add in the battle of smells.
If sink has no garbage disposal leave the squeezed juice stay in the trap, at least overnight. This works for bathroom and bar sinks as well.