After you do the dishes or take a bubble bath you may notice that even after the water has drained, you are left with soap foam in the bottom of the sink or tub. This leftover soap foam can leave soap scum. Soap foam can also be a nuisance when you want to use your sink right after doing the dishes without having to wait for the soap foam to dissipate on its own.
Run your faucet on cold. The colder the water the better. If possible, position your faucet so that the water runs down the sides of the sink.
Fill a cup with the cold water, and working along the edge of the sink or tub, pour the water slowly. You want to work along the edges to coral the soap foam toward the drain. Pouring water over the top of the soap foam in a random way will only scatter it and make it harder to dissipate.
Work your way in toward the drain slowly, using the edges of the soap foam blob as your guide. Keep pouring cups of cold water in this manner until all of the soap foam is gone.
Wipe down the sink or tub with a sponge soaked in warm water once all of the soap foam is gone. Doing this will reveal any soap left behind that you can then rinse down the drain with cold water.