I don't know more ways to explain this is wrong: "but it is not as like as other business income since it is a grant."

It is Exactly like other business income, because that is what it is: Business Income.

Stop thinking that the word Grant makes any difference, unless you find this specific Grant Purposes meets one of those exclusions that I give for examples, and then keep cautioning that you need to investigate if that matters to this client.

Because there are grants under these programs that are not taxable for Fed purposes.

These are Business Income funds. No different than if your client got paid as part of their doing business because that is how and why they qualified to be considered to be given the Grant Money.

"If I enter this amount on SCH C"

Line 1.