On the whole, the average markup on food in a restaurant is around 300 percent. However thi varies by type of restaurant and even the meal or type of food or drink. Here's a few examples of different kinds of markups:
Wine: Twice the retail price and three times the retail price per bottle
Pasta: 600% to 1000% times the food cost
Soft Drinks: More than 1000%
Guacamole: more than 500%
Brunch: 20 times the food cost