I drilled holes in my brick too big for my anchors. How can I fix this?
Use larger anchors/screws. IMO this is the best option.
There are dozens of different types of anchors, so it is possible to find one that will be larger but fit the smaller screw. Myself, I'd drill the rack and use the proper screw for the anchors you have. 

Another possibility, since brick is pretty deep, is to use a longer Tap-Con style screw, like 3" say. You can drill past the old anchor point, but still have plenty of meat for the longer screw to bite. 

Sure, you can plug the holes with wood but I would not trust a bike rack or similar item hung off such a makeshitft anchor.