I have water coming up the bathroom sink drain, it is cold I believe it is from the central air condensation. How can I fix this?

Is there a toilet or tub in this bathroom and does it get any of this water? Central air does have a condensate drain but it is usually near the coil in your furnace. Whatever the water is doesn't really matter much, your drain is clogged. Remove the trap catch the trap water in a bucket. Rod the lateral drain pipe going into the wall with a 1/4" rod, you'll hit a 90 elbow about 8 " inside and then resistance will drop. Rod as far in as you can. Come back and tell us how it went.