I was always instructed to put cereal in the bottle by family members so that the baby could sleep longer at night. This is a myth, and it also makes your baby dependent of a cereal formula bottle right before bedtime. If these conditions are not met at certain point, your baby will actually refuse to go to bed unless his/her expectations are met.
A plain formula bottle will do for the last feed of the night. By 5 months you can start to slowly introduce baby cereal into his meals by mixing with formula in a bowl. If you were to try adding cereal to the bottle, most bottle nipples are not made to pass cereal so you'd need stage 3 nipple and test it yourself to make sure the formula with the cereal flows freely.
If your baby will eat the cereal with a small amount of formula or apple sauce baby food, you should do that instead. If you have a baby who refuses to eat it, you can also try a sippy cup which can be used by the time the baby can sit up (6 months and older) with formula.