We are pretty sure this is the warehouse beetle Trogoderma variabile. They aren't coming from the sink, but are attracted to the moisture and light in the kitchen.
Our entomologist is 99% sure it's Trogoderma, which is in the group of dermestid beetle. Beetles in the family Dermestidae include the carpet, hide, and larder beetles. Although most of these beetles feed on animal proteins, some also feed on high-protein plant materials. In the pantry, they may be found in powdered milk, dried meats, or pet foods that contain fish meal or other animal byproducts.
Dermestid beetles in the genus Trogoderma are general scavengers, but often develop on plant materials such as seeds, nuts, herbs, spices, and cocoa. Some are important pests of stored foods.
The most important step to take to manage an existing infestation of dermestid beetles is to locate and then eliminate any site where they are developing. Evidence of discarded skins of larvae and living larvae are often what is most closely found that can identify a site of breeding insects. Adult insects may wander a considerable distance from breeding sites.
Insecticides should only be used in combination with efforts that provide a thorough clean-out of potential breeding sites and vacuuming/removal of existing insects. Alone they will not effectively manage dermestid beetles.
In managing an existing infestation of dermestid beetles there may be some value in using insecticides to supplement control methods. In nonfood areas household formulation of various pyrethroid insecticides can be applied as sprays. Use of these insecticides must be made strictly in accordance to label directions. Most indicate that applications are applied to cracks and crevices, such as baseboard areas, corners, edges of carpeting and other areas where lint and other debris accumulates. Several over-the-counter insecticides that allow such use are sold through retail outlets and contain as the active ingredient either permethrin, bifenthrin, deltamethrin, cypermethrin, tralomethrin and/or related compounds. (Note: Household “bug bombs” will not be effective against dermestid beetles.) It may be beneficial to hire a pest control company.
Here are some resources that may be helpful.