The best (for medical effectiveness) are pills or capsules. If the pill doesn't have an outrageously obnoxious flavor and if the cat has a soft spot for a particular kind of canned cat food, using an inexpensive pill crusher from the drug store, you can crush the pill into powder and mix it into a small, appetizer-size portion of the yummy food (your cat) doesn't get as her main diet. Or try tuna, chicken, beef, anchovy paste, Cheese Whiz, salmon cream cheese, smooth peanut butter, plain yogurt; all depending on what the cat thinks is fabulous. Ask your vet if the pill can be crushed, some pills are not effective if crushed.
For cats for whom this doesn't work, you can certainly use a pill gun, available at the vet office, online and at some pet stores. Remember to flush the pill down with a bit of water, tuna juice or clam juice. Even when piling by hand, you need that liquid chaser so pills don't stick in your cat's throat.
Some Medications are available in a cream/ointment format that you rub on the inside of the ear.
Professional Pet Sitting Services offered in the Upper to Mid-Pinellas County Area