He cannot sync his iPod touch to your iTunes library without it erasing all the content on his iPod. An iPod touch or other iOS device can only be synched to one iTunes library at a time. Nor would it be legal for you to give him a copy of music that he has not purchased. If he wants the track, he should see if it's available in the iTunes Store and if so buy it. If it's not, he can look to other download stores such as Amazon, Spotify, etc.