What is the nutritional value in eating fruit bats?

Well, they're meat. More or less the same as mice. I would advise against eating them, though, as many bats carry rabies.

There are many kinds of bats you do not want to eat:

Brick bats.  Broken hunks of brick that sometimes come flying at you during political discussions.

Baseball bats.  Solid hunks of wood that come swinging at you during political discussions.

Ding bats.  Semi-literate people who come screaming at you during political discussions.

Bats in the belfry.  See ding bats.

Batting eyelids.  Semi-ethical people who try to get you to take their side in a political discussion.

Cricket bats.  Baseball bats only as British as Gilbey's Gin.

Wom-bats.  Australian marsupials who are generally smart enough to avoid politics.