It may sound odd using produce to produce electricity, but it’s definitely possible. Granted, it wouldn’t be very practical to carry a bag of lemons around to charge your mobile phone, but as an experiment, it’s great fun.
The “lemon battery” uses the juice inside as an electrolyte, and galvanized nails are inserted as electrodes. Wires are then connected to the lemon, and if a group of lemons is wired in series, the collective lemon battery can be used to power a small LED light. According to Wikipedia, the typical voltage output of one lemon is 0.9 volts. Not exactly “shocking”, but certainly interesting!