The brushless ones will work as alternators, just connect the leads to a 3-phase full wave bridge rectifier to convert the AC into DC. Voltage will depend on the RPM and the KV rating of the motor. For example, a 1000 KV motor will have to be turned 1000 rpm to generate 1 volt, 6000 rpm to generate 6 volts.

If you only need to power lights, there is no need to convert the AC to DC, just hook the lights up between any two of the three leads.