Amasty's Special Promotions Pro has worked for me in the past.
(Using Magento 1.9.x) One way to try and achieve this without extra extensions would be to use a Shopping Cart Price Rule
as such:
RULE INFORMATION:
- Rule Name should be the Value of "Free" Product (see below)
- Coupon is set to
No Coupon
- this will let it auto activate when
conditions are met
- Priority is set to
0
- this will ensure it overrides any other
discounts with lower priority
CONDITIONS:
- Set to
All
are True
Subtotal
- is - Equals or Greater Than
99.00
ACTIONS:
- Apply
Fixed Discount Amount
- Discount Amount
XX.XX
(value of product eligible for free purchase)
- In
Apply the rule only to cart items matching the following conditions
you should set: All
are True
& SKU
- is one of
- ENTER SKUs that match value of discount
You would need to create this for every different value associated to the products you have for sale. It's tedious and would need to be constantly updated when new product comes available.
C4B_Free Product extension
once..... – Baby in Magento Aug 17 '17 at 5:35