You could raise the lowest tax rate, that would be a good thing but it would only effect the people who already pay taxes. Better thing would be to eliminate the GST which would benefit everybody who buys anything. You can pay for it by adding some tiers to the tax system on top.

UBI is a cash injection whether you call it that or not. As I said you could achieve similar outcomes by giving people the essentials for free at least up to some threshold. The government could set up a public utility to provide electricity, bandwidth, water, etc and could provide the first X units for free and charge for the rest at market rates or just provide them at cost plus basis. This would force private companies to compete and lower prices for everybody. Similar things can be done for food or rent.

I can even envision a scenario where the government builds facilities like dormitories where you get a room, a bed, a desk and a shared bathroom. You cram these into buildings and offer them as public housing. People living there don't pay for electricity or water or sewer or anything. Minimal and basic but free. As you build more you lower the eligibility requirements until one day every citizen can live in a tiny dorm room for free if they want.