Quick-pickled vegetables and an easy Sriracha-mayo sauce lend Vietnamese flavors to this meatball sandwich recipe. If you can't find long whole-wheat sandwich rolls, you can use 5-inch slices of a soft whole-wheat baguette from the bakery.
Combine vinegar, honey, and salt in a medium bowl. Add cucumber and carrot; let stand at room temperature for 20 minutes or refrigerate for up to 24 hours. Drain off the marinade.
Combine mayonnaise and Sriracha in a small bowl.
Place meatballs in a microwave-safe bowl; cover and microwave on High until just warmed, about 2 minutes.
Spread half of the mayonnaise mixture on each roll. Divide the meatballs and the vegetables between the rolls. Sprinkle with cilantro.
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