Is it Keto?
List of popular items and whether they are ‘keto-friendly’.
First, I have to say you MUST look on jars and cans (unless it actually says ‘keto’) rather than rely on keto lists or books, which are fine for fresh stuff, although things like tomatoes, fruit, sweetcorn can be a bit tricky due to the variable sweetness.
Many things are no problem cooked as granny used to but the food industry will insist on adding things to tempt us taste wise and sugar is one of them. Tomato sauces are a classic example.
Tip: Buy from the stores own basic brands. Always check but they tend not to add sugar as they do with their more expensive branded counterparts.