In a small bowl, combine apple cider vinegar, sugar, corn starch and mix thoroughly until the corn starch and sugar dissolve. Set aside.
In a wok/ large frying pan, heat the oil on mediumhigh heat and fry the garlic-ginger mixture until fragrant.
Add the prawns and cook until they slightly change color and add the tomato paste. Toss thoroughly.
On high heat, add tomatoes wedges and cook until they slightly wilt. Add cucumbers, bell pepper and snap peas in one-minute intervals.
Add the stir-fry sauce by the spoonful. Toss around, make sure everything is well-coated. Add the salt and season to taste.
Remove the pan from the heat when all the sauce is incorporated, and the cucumber is opaque.
Garnish with cilantro and ground black pepper. Serve hot with rice.