Before getting rid of the rabbits, do a thorough search of the garage. Check the baseboard area and the walls for any holes or cracks a rabbit might fit through. Block or repair those holes. How you block or repair a hole will depend on the nature and size of the hole. You can also place rabbit repellent in the areas you believe rabbits come through to get into the garage. Rabbit and small animal repellent is available at hardware and farm supply stores. Close any open windows. This step may be enough to keep rabbits out if they only visit the garage occasionally and aren't nesting inside.
Get a small, live animal trap (or multiple traps if you have many rabbits to catch). If you have seen the rabbits in your garage or yard, you'll be able to estimate the size of trap necessary. Basically, it must be large enough for a rabbit to enter and stand inside. Live traps are designed to lure the animal inside with food. When the rabbit steps into the cage of the trap where the food is, the door immediately closes, leaving the rabbit trapped inside.
Set the trap(s) in the garage on the floor. If you have seen where the rabbits entered the garage, you can set traps nearby. Use food rabbits like, such as lettuce or other vegetables (rabbits are herbivores), as bait. Set the trap according to the package directions. Stay out of the garage and keep pets and children out until the rabbits are trapped. You may need to set the traps for multiple days until they are caught. Check the traps each morning and if a rabbit is inside, you can take it outside and let it go. Wear gardening gloves to be cautious. You can also consult your local animal services department (if your city has one) and ask what is recommended.
Prevent rabbits from entering your garage by sealing all cracks and holes in the floor, walls, and roof. Check your vehicle before parking it in the garage if it has been parked outside where rabbits may have entered under the hood or next to the tires. Rabbit repellent also prevents rabbits from entering your space. It does not poison the animals but emits an odor they find unpleasant, keeping them away. Keep any food stored in the garage tightly sealed in hard, plastic containers (not boxes, which rabbits can chew through).