If water is dripping onto the floor of a cabinet below a sink, leaky supply tubes may be the cause. More likely, however, a stop valve or supply-tube connection is the culprit.
To find the source of a leak, shine a bright flashlight into the cabinet and feel the pipes and tubes, stopping to dry your hand every so often. You can also dry the area, place dry newspaper under the suspect plumbing, and watch for spots of water.
A solid chrome-plated copper supply tube looks and feels more stable than a flexible braided tube. But the solid tube is actually more likely to develop a leak because it is inflexible. When bumped a braided tube is less likely to be damaged. Still many people prefer the appearance of a solid tube.
Less than an hour to tighten nuts or install a new supply tube
Adjustable wrench, basin wrench, tubing bender, tubing cutter
Measuring and cutting a tube, connecting a compression fitting
Place a bucket or towel below the leaking plumbing; make the area comfortable for working.
Solid or braided supply tube
If water leaks at the stop-valve spout, use an adjustable wrench to tighten the nut that connects the supply tube to the valve. (If the valve moves, brace it with another wrench.) If water leaks from where the supply tube enters the faucet, tighten the nut with a basin wrench.
At the upper end, slip on the mounting nut and a ferrule. Poke the tube into the faucet inlet, slide the ferrule up to the inlet, and tighten the nut. Slip a nut and ferrule onto the lower end of the tube and attach to the stop valve in the same way.