Don’t underestimate regular tap water, it usually contain some amount of needed iron. Otherwhise I would drink one glass of orange juice (to enable a better iron intake).
Of course, you could also make different types of smoothies or shakes.
The cheapest substitute for milk is unfortunately soy milk, occassionally, you might be able to get your hands on almond milk, rice milk, wheat milk, and if you’re lucky even hazelnut milk. Just make sure it is fortified with added calcium and other minerals.