Horses naturally gravitate towards a healthy diet. Nearly all fruits and many different vegetables work wonderfully as treats for horses. Horses traditionally love apples and carrots but also like certain berries, pumpkin, or even snow peas! Vegetables to avoid would be stronger ones like onions, potatoes, cabbage, or nearly any nightshades. They can even be given a few cubes of sugar, as seen in the movies, but that works best given as a special treat and not a snack for every mealtime (source).