We were diverted from Heathrow to Cologne on our return flight from Bangkok on 18th December resulting in an unscheduled 3 day stay at Cologne airport. Initially after a 13 hour flight all passengers were held on Cologne runway in the plane for 3 hours without any information on what was happening. Passengers were finally taken off the plane with only hand luggage. Taiwanese passengers were dumped by the airline on Saturday night at arrivals having no visa to get into Germany. It was only until their tour guide contacted the Taiwan Embassy in Germany for intervention were they allowed through into Germany. Not a great start for a Taiwanese owned airline - Red Cross also had to help to provide beds food and drink for these people as the airline would provide nothing. A few hotel rooms were provided on the Saturday night but this was organised by Cologne airport as Eva air did not put any staff in the airport to care for passengers. As there were insufficient rooms passengers were asked to share with people they did not know and some people were left without. On Sunday a representative from Eva air arrived and provided some assistance and a hotel on Sunday night. Sunday evening was the first time in 20 hours that we were given food and drink by the airline. On Monday we were advised our departure time would be 1830. We were then delayed and held at the gate until midnight and then finally allowed to board - at 0100 on Tuesday morning we were advised by the pilot that our departure slot had changed to 0520. By 5:30 running water facility on plane was no longer available creating in sanitary conditions and at for 60 to 90 minutes the air conditioning was turned off leaving passengers to sit in the clothes they had been in for the past 3 days as no access had been made to stowed luggage. It is also important to realise that at this point several passengers who had medication in the hold were becoming ill one requiring paramedics to board the plane as they had not been given access to their luggage since departing from Bangkok or Taipei. Intervention from other passengers appeared to be the only way of helping these people. Finally at 08:40 our plane departed. Would I ever fly with Eva again? It is highly unlikely.