What is the best way to sedate a cat?
Through your vet. Usually if you put the cat in a cat carrier (you can buy these second-hand at dog grooming places at a considerable lower cost and then sanitize it) there is no need for sedation before taking the cat to the vets. If you are going on a plane, some planes allow the pets under your seat (don't know if this still applies so you'd have to ask). If traveling by car or have the cat in a camper then your vet will know how much your cat will need and how long the sedation will last.
Certainly not every day, but if you have to travel with the cat then see your vet and they will give you the right sedative to give your cat (which goes by age and weight.) It is kinder to sedate a cat that is not use to traveling (if you are moving or going on a holiday) than not. Most sedatives prescribed by a vet only are quite safe.
You cannot sedate your cat without paying for a vet. If you would like a light sedation for things such as traveling, you can ask your vet about using Acepromozine. I use them for one of my animals during thunderstorms. It is a light sedation pill which is fairly inexpensive. It helps calm the cat, but it does not make the cat sleep.