I see now that I actually did a fairly terrible job at responding to the original question.
Has anybody of you taken a cat in the cabin and if so, how did you handle everything (at the airport, check-in and control, water, etc.)
It seems that my cat has to stay only 10 days in the quarantine station (we've already began the vaccination and all the procedure). Landing is in the afternoon - do you know if the cat is brought to the quarantine station the same day or does she have to stay till the next day in Changi?
Carriers - can buy at any pet store. Get a soft one that fits Lufthansa's guidelines (they smoosh under the seats better and are lighter to carry). Or try Amazon.de.
Check-in - book cat reservation, pay fee, notify check-in agent, sometimes get a little tag for the carrier from agent.
Customs - have to take cat out of carrier to go through x-ray (duh), put blanket over him if he's skittish, or put a leash on if he's prone to run. Put carrier on belt, walk through metal detector, get carrier, put cat back in carrier, continue on your way.
Water - bring small bottle and bowl, offer to cat at layover. Cats are sometimes too freaked to eat or drink, which is ok, just make sure cat eats every 24 hours. Wet food is helpful as it's 80% water, so two birds with one stone.
Quarantine - I've read that animals arriving before noon go same day, others wait until following noon transfer. Not sure if this is really the case. I need to check into this myself.
Paperwork - do NOT mess with Singapore regulations. Do exactly what they ask to the letter or you will likely wish you had. Have all original signed papers with all requirements fulfilled precisely as described. Seriously, they really follow the rules here and will not be pleased if you do not. I cannot stress this enough.
MISC - do not sedate your cat unless he is a total monster. It's not safe or recommended by AVMA or the airlines. Do not mess with your cat while he's on the plane. Cats sleep 16 hours a day. Let him settle down and rest. He may complain during take-off/descent like babies do, as the pressure change annoys him. Let him complain a little then he will calm down on his own. You will likely be more upset than he is. My cat is a spoiled, whiny little sucker but when animals are stressed it's best to let them cope on their own rather than trying all manner of tactics to calm them which will likely be counterproductive. Depends on the cat of course, but what makes you feel better may not make him feel better.