In aqueous solution the correct order of acidity of the alcohols is

In water the alkoxide of the smaller alcohol is better solvated by hydrogen bonding, because the large alkyl groups of $(\mathrm{CH}{}_3){}_3\mathrm{CO}{}^{-}$ hinder solvation. Therefore methanol is the most acidic ($\mathrm{p}{K}_a$ about 15.5) and tert-butyl alcohol the least (about 18).