A hotel in Denmark is offering a free meal to any guest who produces electricity for the hotel on an exercise bike attached to a generator.
Guests will have to produce at least 10 watt hours of electricity - roughly 15 minutes of cycling for someone of average fitness. They will be given vouchers worth 26 euros ($US36).
The Crowne Plaza Hotel in Copenhagen says the idea is to get people fit while reducing their carbon footprint.
The BBC reports the hotel already produces renewable energy with solar panels on its facade.
The offer will be launched on 19 April and run for a year. Only guests staying at the hotel will be able to take part.