Submerge the cucumber, carrots, and onion in a bowl with vinegar. Mix well and let sit until ready to use, (about 5 to 10 minutes). Drain well before using.
In a bowl whisk together the sweet chili sauce, mayo, and ketchup. Season with salt and pepper to taste.
Lightly toast the bread. Spread the mayo mixture onto both sides of the bread.
Layer the bread with Spring mix, roast beef, pickled vegetables, and cilantro. Serve with pickle and chips.