Sacrifice a Food: Target creature blocks Maraleaf Rider this turn if able.
If the target creature can’t block for any reason (such as being tapped), then it doesn’t block. If there’s a cost associated with having it block, its controller isn’t forced to pay that cost, so it doesn’t have to block in that case either.
If the target creature can block other creatures but can’t block Maraleaf Rider, it’s free to block any other creature or to not block at all.
If an effect refers to a Food, it means any Food artifact, not just a Food artifact token. For example, you can sacrifice Gingerbrute to activate the last ability of Tempting Witch.