A kitchen sprayer that barely dribbles or will not switch from stream to spray is almost always a clogged spray head or a kinked hose under the sink. Mineral deposits block the tiny spray holes over time. The retractable hose gets kinked when items stored under the sink push against it. A failed diverter valve (the part that switches water from the spout to the sprayer) is the third possibility. All three are easy fixes -- 10-30 minutes, no plumber needed.