This is a guide on how to repair your light if you have had it for a few years and the stress of the outdoors have caused it to stop working.
Honestly, why won't cheap things last longer than five minutes?
Step 1: Take Apart the Light Fitting.
First of all, you need to take apart your light fitting. Usually most lights will be held together by screws around the edge. Just look on the underside and remove any that you find. The glass or plastic cover for the light sometimes twists apart aswell so try that too.
After you have opened it, just take off any big removable parts, taking note on how they assemble so you can fit them back on. Also remove the batteries if they are rechargable. If they are physically attached / soldered in, just leave them as they are.