When acids react with acid you get displacement reaction taking place in which hydrogen and a salt are formed. How vigorously they react depends on their reactivity, which you can check out in the reactivity series. Metals like sodium, near the top of the reactivity series, react dangerously fast.
Alkali metals react widly with water, with the rate increasing with the atomic weight of the alkali. An alkali metal hydroxide and hydrogen gas are formed.