The answer
9,000dollar bills
Thirteen litres of hard case. Nine thousand bills is nine hundred thousand dollars in hundreds — so the briefcase of a million, in every film you have seen, is quietly too small.
Crammed No. 29 ran on September 25, 2026. Source: interior of a hard attache case, 46 x 33 x 12cm outside.
Answers are given to two significant figures.