。
Mother made us cheese sandwiches for lunch.
Literal
Mother [subject-が] lunch [for-に] us [to-に] cheese-sandwich [obj-を] made-for-us.
Three different に's in one sentence: 昼食に (time/context: 'at/for lunch'), 私達に (recipient of the benefit: 'for us'), and the implicit 作ってくれた. Japanese doesn't mind stacking に for different functions — each particle is unambiguous from its position and the verbs it relates to.