Mix the flour, baking powder and salt together in a bowl. Slowly add the water and keep stirring until you have a smooth batter. Mix about 6 tablespoons of the pineapple syrup with the stock or water, cornflour, ketchup, fish sauce and sugar or honey in a small bowl until smooth.
Heat 7 cm (3 inches) of oil in a wok over a medium heat. It is ready when a little batter sizzles immediately when dropped in. Coat half the pork in the batter and lower each slice into the oil. Deep-fry for 4–5 minutes or until nicely browned. Drain on kitchen paper. Repeat with the remaining pork.
Remove most of the oil, leaving 1½ tablespoons in the wok, and stir-fry the garlic over a medium heat for 1–2 minutes or until lightly browned. Add the carrot, onion, pepper and stir-fry for 3–4 minutes. Add the cucumber, pineapple, tomato and pineapple syrup mixture, and stir together for 1–2 minutes. Taste and adjust the seasoning. Return the pork to the pan and gently mix with the sauce.
Spoon on to 4 warm serving plates and garnish with coriander leaves.