Baby formula is a protein-based stain. Protein stains are animal based in nature and require careful attention to prevent damaging the garment.
If the spot is on white clothing treat the stain with undiluted lemon juice and place the item in the sun to dry.
Most likely, the stain is on a colored fabric or shirt. To treat the stain on colored clothing, coat the spot with a paste made of cool water and unseasoned meat tenderizer and let stand for at least 30 minutes. Once dry, brush away the paste and launder as usual.
Soak in an enzyme solution according to the item's and manufacturer's instructions.
In a pinch, wipe formula spills and spit-ups with moist baby wipes. Rinse with cool water, then treat any remaining stain as quickly as possible.