So this is a dumb problem to have. My little brother decided to do something nice and wash my car for me while I was sleeping. It looks like he used the rough side of a sponge on my one headlight, so it looks like garbage compared to the other one which is basically like new.

What's the easiest/cheapest way to get it looking like new again?

 

Darkside,

Ouch. Sorry to hear about the damage inflicted upon your ride thanks to your bro's clandestine cleaning job Thank goodness he didn't decide to take it one step forward and wax your Civic!

As for restoring the aesthetic quality of your Civic's headlight, there are many high-quality plastic headlight lens restoration kits available. I recommend purchasing the Meguiar's G1900K headlight and clear plastic restoration kit or the 3M headlight restoration kit. Typically, these kits include a polishing orb that you place on the end of a power drill as well as chamoises and the cleaning agent itself. Read the instructions carefully because you could possibly further damage the headlight if you operate the drill at too high of a speed. The entire process takes a few minutes and the results are quite impressive.

While you're addressing the exterior marring of the headlight it would also be a good idea to remove the units and clean out any moisture that may have occurred inside of the assemblies. I'm not sure if your Civic is like mine but I have accumulated quite the king's ransom of dirt and moisture inside of my headlight lens within a matter of a few years. When cleaning out the inside of the headlight, use a microfibre towel and a good quality glass cleaner thoroughly on the affected area.

For your reference, here's a diagram illustrating the bolts that must be removed in order to access the inside of the headlight:


*diagram courtesy of hondapartsnow.com; all rights reserved

 

you can buff them out.
you need to get 1000 grite wet sand paper, rubing compound and wax, masking take and a buffer (high speed is better)
first you put tape all arround the ligth so you dont damage the paint in your bumper, grill etc.
then you sand all the rough surface, use lots of water. make sure you get all out.
then you use the rubing compound.need to use a buffer, use water too to make it easer.
then apply your wax with the buffer will be ease but can do it with the hand too.

they will look brand new again

 

Meh....buffers require money. If you don't have one, a repair can add up quick. I detail quite a bit on the side (not to toot my own horn) so I have a few tricks. If you want a cheaper repair to using a buffer...try this.

Sand the headlights down. I'd start with 600 or 800 and work my way up to 1500. Then you spray on 1k clear in an aerosol can. Here is a thread on it.

Understanding headlamp repair - Auto Geek Online Auto Detailing Forum

Amazon.com: SEM 40903 - 1K HS Clear - High Performance Clearcoat: Automotive

It does work, it's just not normally my method of doing it because it requires headlight removal (which on a civic isn't difficult). I normally sand from 800 to 2000. then use compound and polish on various pads with a buffer. Finally i coat the lens with CQuartz.