As a feeding specialist I generally don't advise using food rewards or "treats" because it causes kids to covet these food items and see other foods (usually healthy foods) as less desirable. BUT! I think I found a way around this. (I started this when my daughter was around a year so maybe an older child would be less inclined to cooperate with this technique...but if you start early and lay the foundation when your kiddo is little, many will take it at face value. For us, it still works well now that my daughter 2.5 years old!) So, I walk around with a healthy snack and don't offer any to my daughter. I wait until she shows some interest then I tell her it's a special snack- a "treat!" I say. If she's still interested, which she always is, I say, "ok I'll share with you." Then I share my health food item with her. She is hooked every time. Totally drawn in and excited to try what I've got. That may be some roasted butternut squash, or fresh snap peas, or seaweed. Sometimes it is something the average person would consider more of a "treat," like chocolate covered sunflower seeds, or blackberries but not always. Sometimes it's home roasted pumpkin seeds with sea salt, garlic and cumin. A really "treat" in my book.
Case in point: the other day her very special "treat" was freeze dried sardines. She loved these "chips" and carried around a small bowel of them for a while. (Yup, she is naked, outside, in an Honest Co box, eating sardines. That's how we roll.)
This might not be my very finest feeding advice, but I'm curious to hear if this little gem works for you! We really need to get away from junk food and sugary desserts being synonymous with "treat" and teach kids that delicious, home cooked or store bought but healthy foods can qualify as a "special treat."