What needs fixing:
需要修正的地方：
Batter is too thin. Flour + egg + water (no leavener, no cornstarch) will produce a dense, heavy, cake-like coating that turns soggy quickly, not the light, crispy, shattery crust you want for this dish.
面糊太稀了。面粉+鸡蛋+水（没有膨松剂，也没有玉米淀粉）做出来的涂层又密又重，像蛋糕一样，而且很快就变软，不是你在这道菜里想要的那种轻薄、酥脆、易碎的 crust。
Sauce is unbalanced. You call for vinegar + pineapple juice with no added sweetener except what's in the pineapple. That will be aggressively sour and thin—more like a vinaigrette than a glossy, sticky sweet-sour sauce. Classic sweet & sour needs sugar (brown or white) to balance the acid.
酱汁味道失衡。你只用了醋和菠萝汁，除了菠萝里的糖分外没有加任何甜味剂。那会非常酸而且稀——更像油醋汁而不是光泽诱人、黏稠的甜酸酱。经典的甜酸酱需要糖（红糖或白糖）来平衡酸味。
Missing aromatics. Garlic and ginger are the backbone of Chinese-style sweet & sour. Without them, the sauce tastes flat and one-dimensional.
缺少芳香料。姜蒜是中式甜酸菜的灵魂。没有它们，酱汁尝起来平淡无味、缺乏层次。
Cornstarch slurry technique is vague. You say "stir until it thickens," but if you add cold slurry to a simmering liquid, it can clump or fail to thicken if not heated properly.
玉米淀粉糊的用法描述得比较模糊。你说“搅拌至变稠”，但如果把冷的淀粉糊加到微沸的液体中，如果没有充分加热，很容易结块或者起不了稠度。
Vegetable choice is limited. Green pepper and pineapple alone are fine, but onion (or scallion) adds textural contrast and sweetness.
蔬菜选择有点局限。青椒和菠萝单用没问题，但加点洋葱（或小葱）能增加口感层次和甜味。
Sauce quantity isn't given. You don't mention how much vinegar, juice, or cornstarch—so a cook has to guess.
没给酱汁的用量。你没提具体要用多少醋、汁或玉米淀粉，导致做饭的人只能靠猜。
"Consistency of salad dressing" is misleading. Sweet & sour sauce should be glossy, thick enough to coat the back of a spoon, and cling to the pork—not runny like vinaigrette.
“沙拉酱的稠度”这种说法有误导性。甜酸酱应该是光泽的，浓稠到能挂在勺背上，并且能裹住猪肉——而不应该像油醋汁那样稀。
Tossing pork too early. If you toss the crispy pork into the sauce and then serve immediately, it's fine. But if you let it sit, the crust will steam and turn chewy. The recipe should warn to serve right away.
猪肉拌得太早了。如果你把脆皮猪肉拌进酱汁里马上端上桌，那没事；但如果放一会儿，外皮会被蒸得变软发韧。食谱应该提醒要立即食用。
Buttered rice is a Western touch—perfectly fine, but not traditional. (No need to change unless you want to be authentic.)
黄油米饭是西式吃法——完全没问题，但不算传统。（除非你想追求正宗，否则没必要改。）
Fixed & Improved Recipe
修正并改进后的食谱
Sweet & Sour Pork (serves 4)
咕噜肉（4人份）
For the pork & batter:
猪肉与面糊部分：
1 lb (450 g) boneless pork loin or chops, cut into ¾-inch cubes
1磅（450克）去骨猪里脊或猪排，切成约3/4英寸的方块
½ cup cornstarch (or potato starch)
1/2杯玉米淀粉（或土豆淀粉）
¼ cup all-purpose flour
1/4杯中筋面粉
½ teaspoon baking powder (for extra crispiness)
1/2茶匙泡打粉（增加酥脆度）
½ teaspoon salt
1/2茶匙盐
⅛ teaspoon white pepper (or black)
1/8茶匙白胡椒粉（或用黑胡椒）
1 large egg, beaten
1个大鸡蛋，打散
⅓ cup cold water (or more as needed)
1/3杯冷水（或按需添加）
Neutral oil (e.g., peanut or canola) for deep-frying
中性油（如花生油或菜籽油），用于油炸
For the sauce:
酱汁部分： 3/4杯菠萝汁（从罐头中预留）
¾ cup pineapple juice (reserved from the can)
¾杯菠萝汁（从罐头中预留）
¼ cup rice vinegar (or white vinegar)
1/4杯米醋（或白醋）
¼ cup packed brown sugar (or granulated sugar)
1/4杯红糖（压紧量，或白砂糖）
2 tablespoons ketchup (adds color and mild sweetness—optional but classic)
2汤匙番茄酱（增加色泽和温和的甜味——可选，但很经典）
1 tablespoon soy sauce (light)
1汤匙生抽
2 teaspoons cornstarch mixed with 2 tablespoons cold water (slurry)
2茶匙玉米淀粉混合2汤匙冷水（制成淀粉糊）
For the stir-fry:
炒制部分：
1 tablespoon oil (for the wok)
1汤匙油（用于炒锅）
2 cloves garlic, minced
2瓣大蒜，切碎
1 teaspoon grated fresh ginger
1茶匙新鲜姜末
1 medium green bell pepper, cut into 1-inch strips
1个中等大小的青椒，切成1英寸长的条
½ medium onion, cut into wedges (optional, adds sweetness)
1/2个中等大小的洋葱，切成楔形（可选，增加甜味）
1 can (8 oz / 225 g) pineapple chunks, drained (reserve juice)
1罐（8盎司 / 225克）菠萝块，沥干（预留果汁）
To serve:
上桌搭配：
Steamed jasmine rice (omit the butter, or serve on the side if you prefer)
蒸茉莉香米（省略黄油，或者如果你喜欢，可以分开盛放）
Method
Prep the pork. Pat the pork cubes dry with paper towels. In a medium bowl, whisk cornstarch, flour, baking powder, salt, and pepper. Add beaten egg and cold water, whisking until you get a thick, smooth batter that coats a spoon (like thin pancake batter). Add a splash more water if too thick.
准备猪肉。用厨房纸巾吸干猪肉方块表面的水分。在一个中等大小的碗中，将玉米淀粉、面粉、泡打粉、盐和胡椒粉搅拌均匀。加入打散的鸡蛋和冷水，搅拌直到形成浓稠顺滑的面糊，能挂在勺子上（类似稀煎饼面糊的稠度）。如果太稠，再加一点点水。
Heat the oil. In a deep pot or wok, heat 2 inches of oil to 350°F (175°C).
加热油。在深锅或炒锅中，倒入2英寸深的油，加热至350°F（175°C）。
Fry the pork. Dip each pork cube into the batter, letting excess drip off. Fry in small batches (don't crowd) for 3–4 minutes until golden and crispy. Drain on a wire rack set over a baking sheet. Keep warm in a 200°F (95°C) toaster oven or regular oven while you finish.
炸猪肉。将每一块猪肉蘸上面糊，抖掉多余的面糊。分批油炸（不要 overcrowd 挤在一起），炸3–4分钟至金黄酥脆。放在铺在烤盘上的wire rack（ wire rack：金属晾架）上沥油。在继续制作酱汁的过程中，将猪肉放在预热至200°F（95°C）的烤面包机或普通烤箱中保持温热。
Make the sauce. In a small bowl, combine pineapple juice, vinegar, brown sugar, ketchup, and soy sauce. Stir well. In another small bowl, make your cornstarch slurry.
调制酱汁。在小碗中混合菠萝汁、醋、红糖、番茄酱和酱油，搅拌均匀。在另一个小碗中准备玉米淀粉水。
Stir-fry. Heat a wok over high heat until smoking. Add 1 tablespoon oil, then garlic and ginger—stir-fry for 15 seconds until fragrant. Add green pepper and onion (if using), and stir-fry for 1–2 minutes until bright and slightly tender but still crunchy. Add the pineapple chunks and toss for 30 seconds.
翻炒。大火加热炒锅直至冒烟。加入1汤匙油，然后放入蒜和姜——翻炒15秒至出香味。加入青椒和洋葱（如果使用），翻炒1-2分钟，直到蔬菜颜色鲜亮、微软但仍保持脆爽。加入菠萝块，翻炒30秒。
Thicken the sauce. Pour the sauce mixture into the wok. Bring to a boil, then reduce to a simmer. Give the cornstarch slurry a stir and drizzle it in while stirring constantly. Cook for 30–60 seconds until the sauce turns glossy, thick, and coats the back of a spoon—not like salad dressing, but like warm maple syrup.
收浓酱汁。将调好的酱汁倒入炒锅中。大火煮沸后转小火慢炖。搅拌玉米淀粉水，一边持续搅拌一边缓缓倒入。煮30-60秒，直到酱汁变得光亮、浓稠，能挂在勺背上——不要像沙拉酱那样稀，而要像温热的枫糖浆那样浓稠。
Combine and serve immediately. Turn off the heat. Add the warm crispy pork to the wok and toss quickly to coat each piece with sauce—about 10 seconds. Do not over-stir, or the crust will soften.
混合并立即装盘。关火。将热乎酥脆的猪肉加入炒锅中，快速翻拌让每块肉都裹上酱汁——大约10秒。不要过度搅拌，否则脆壳会变软。
Serve right away over hot steamed rice.
趁热盛出，浇在热米饭上食用。
Why this works better:
为什么这样做效果更好：
Crispier pork – cornstarch + baking powder = light, shattery crust.
猪肉更酥脆——玉米淀粉+泡打粉=轻盈、易碎的脆皮。
Balanced sauce – sugar + ketchup tame the vinegar, giving sweet-tangy harmony.
酱汁平衡——糖+番茄酱中和了醋的酸味，带来甜酸和谐。
Aromatics – garlic and ginger add depth.
香料增味——蒜和姜增添了风味层次。
Proper thickness – glossy, clingy sauce that coats, not runs.
浓稠度适中——酱汁光亮、挂壁，能均匀包裹食材而不流淌。
Timing – pork stays crispy because it's added at the very end and served instantly.
时机掌握——猪肉在最后阶段加入并立即上桌，从而保持酥脆。
This version honors your memory of the dish while fixing the technical flaws.
这个版本尊重了你对这道菜的回忆，同时修正了技术上的缺陷。