The best plan to prevent Russia from winning would be to cut off Russia's oil revenue. Fossil fuel exports are the only way that Russia can sustain their war effort. First, other European countries need to get serious and stop buying from Russia. Second, give Ukraine enough long range missiles to wreck Russia's fossil fuel infrastructure: pipelines, tank farms, refineries, ports, etc. Russia was heavily dependent on foreign technical experts to maintain that infrastructure and has little capacity to do so on their own.

This can be done with very little US funding. And sharing intelligence with Ukraine literally costs us nothing.