Some examples:
apple, banana, mango (comma separate foods)
pepperoni pizza*3, banana*0.5 (multiply by quantity)
Wendy's double with cheese (more specific is better)
Some examples of 1 serving size
3 oz meat
1 cup cherries
8 oz liquid
1 oz nuts
1 cup pasta
1 cup vegetables
1 cup broccoli
1 cup rice
1 oz chips (~10)
1/4 cup pasta sauce
2 tbsp dressing