No airline will allow you to transport the cat in the cabin. I guess you're not flying KLM (as you have layover in Germany) which is unfortunate, as at Schipol in Amsterdam, KLM has a pet hotel where the animals in transit are checked by a vet, given food/water and access to a litter box. Perhaps you're flying Lufthansa and you could check to see if they have a similar facility.

Getting the import license is not difficult - if you're here. That's why I recommended a pet relocator - they handle the paperwork and meet the flight to smooth any bumps in the road. It's well worth the money.

Giving an animal a tranquilizer or sedative is not usually recommended because if there is turbulence, the animal may be tossed willy nilly with no ability to brace itself.

The cat will be fine in the hold - perhaps even better than in the cabin because there won't be so much activity.

Signature line > "You can't fix stupid"