I would ask someone about their
Or to be slightly more formal
or, as already suggested, inquire about more general
A lot depends on the context; when talking about recipes you don't need to be as careful about allergens, for example.
For those who are not familiar with the OP's use of the terms "veg" and "non-veg", they are standard terms in Indian English for vegetarian and non-vegetarian food; for example a restaurant sign might say "veg and non-veg" to indicate that they cater to people with both dietary preferences.