The car was filthy when he returned it to me, and 'to cap it off' [='to top it off'], there was almost no fuel left in the tank.
a 'shower/bathing cap' [=a head covering that people wear to keep their hair dry when they are showering/swimming]
They may not like being called careless, but 'if the cap fits, wear it'. [=('US') 'if the shoe fits, wear it']
(..) They prefer "dead Confederate sailors whose lives have been given in tribute to Ares." But "zombies" is fine. Reardon! Gun! Faster! Now! Gun is hot, Cap'n. Locked and loaded. Aim it at that meat grinder. Wait, wait. You want to shoot that thing with this? Do you have a better idea? (..)2013 Percy Jackson: Sea of Monsters
(..) to have a thing or two to help you out. Collector's item, mint condition. Best TV show ever. So, of course, cancelled. Got this off Deity-Bay. You twist the cap off this, you release the winds from the four corners of the Earth. Now, you tell me that isn't cool. Whoa! No, not in here! Not in here. (..)2013 Percy Jackson: Sea of Monsters