Final answer:
A strawberry slice is a suitable garnish for appleberry sangria to complement the fruit flavors, although lemon or orange slices and mint leaves are also commonly used.
Step-by-step explanation:
The garnish for drinks such as appleberry sangria can vary based on personal preference or the specific recipe being followed. However, considering the ingredients listed such as cherries, fruit cocktail, fruit salad, and diluted grape juice, a suitable garnish that would complement the fruit flavors might be option 4) Strawberry slice. Strawberries would match well with the other fruits in the sangria and enhance its appearance. Nonetheless, garnishes like lemon slice, orange slice, and mint leaves are also commonly used in various sangrias and can be used depending on what flavor profile you prefer.