My baby, 9 months old, has refused every bottle and every baby formula so far.

Because she has weight gain issue, and I want to give her a formula (which are pretty caloric) + (I'll try with a cup) can I add flavors in it, such as dates, almonds, fruit... just to slightly change the taste and smell?

Is this bad idea? Has anyone tried this?

Thank you!

EDIT: when I mentioned the dates, fruits and almonds, I meant them liquified just as the formula, as fruit puree for an example or so. Not the whole things. 🥴