The truth is that sweet &sour sauce is WHAT YOU MAKE IT.
A good standard recipe is to start off with: 1 tab sugar and one tab of red wine vinegar, 1 tab of cornflour thickening and one tab of soy sauce (first tab thick/dark any later, light), plus your RED FOOD COLOURING, a small dash to give it that deep colour.
Cantonese style: use fresh pineapple, green pepper, carrot rounds, onion quarters, and of course pineapple. Dilute with orange juice.
Chinese vinegar, sugar, cornflour, preserved vegetable (canned), Sezchuan preserved vegetable, some fresh fruit del la saison, bean curd cheese, and a bit of what you fancy. You can add some chilis also if it is not hot enough.
If you want swet & sour, then do that.
Hot&salty, do that.
Tomato, is NOT normally a constituent of a sweet or hot sour sauce, except in the west.