If you create a “leave type” as a “meal allowance” in your attendance template/settings and you add this leave type to your absence calendar – you can create directly (after approval) an expense out of it.
After your created the the leave type (meal allowances) you can create a travel expense instantly:
The Expense name, category as well the amount is already in the expense. Please go on as you would with any other expense. You can find more infos HERE