Mac B., Kid Spy #6: Mac Saves the World by Mac Barnett
From Orchard Books:
The Queen of England calls on her trusty spy, Mac B., once again. This time, Mac must navigate secret tunnels beneath the Berlin Wall in order retrieve cheat codes from a Soviet scientist. Floppy disk in hand, our hero finds himself trapped in East Germany, stuck between the wall and the Stasi. How will he escape? Well it is 1989, and walls do fall down.