A suction cup that doesn't adhere well is frustrating, if nothing else. The suction cup that sticks well to a window may not stick as well on stainless steel if the surface is slightly textured, such as on a brushed stainless steel sink. Petroleum jelly or cooking oil creates a seal beneath the suction cup, helping it stick even to stainless steel.
Clean the suction cups by wiping them down with a damp sponge containing a small amount of dish soap. Rinse the suction cups under warm water while rubbing them with your fingers to remove any stubborn dust particles. Dry the suction cups with a lint-free cloth. Even small amounts of dust or dirt may render a suction cup completely ineffective and unable to stick.
Sprinkle baking soda on a damp sponge. Wipe the stainless steel down thoroughly with the sponge, rubbing dirty areas to remove stuck-on debris. Rinse the sponge, and wipe the stainless steel again to remove baking soda residue. Dry the steel with a lint-free cloth.
Press the suction cups onto the desired area of the sink. Tug down gently on the suction cups or the device they are attached to; if the cups slide or fall off, press them onto the steel again in another area -- a small dent or flaw in the steel may decrease the suction power.
Wait several minutes and tug gently downward on the suction cups again. If they fall off or move, rub a thin layer petroleum jelly or cooking oil over the perimeter of the suction area of each suction cup using your finger or a paper towel. Press the suction cups into place again.