Whisk together red wine vinegar, reserved pineapple juice, sugar, ketchup, and cornstarch in a bowl until well combined.

Heat 1 tablespoon of vegetable oil in a large nonstick skillet over medium-high heat until it begins to smoke slightly.

Add half of the chicken to the skillet and cook, stirring frequently, until it is no longer pink inside, approximately 3 minutes.

Transfer the cooked chicken to a plate. Repeat the process with an additional 1 tablespoon of vegetable oil and the remaining chicken.

Add the remaining oil to the now-empty skillet, followed by the salad bar vegetables. Cook until the vegetables have softened, about 4 to 6 minutes.

Introduce the pineapple chunks, minced garlic, and grated ginger to the skillet. Cook until the garlic and ginger become fragrant, approximately 1 minute.

Pour the vinegar mixture and the cooked chicken, along with any accumulated juices, into the skillet. Simmer until the sauce thickens, around 2 minutes.

Serve the sweet and sour stir-fried chicken immediately.