Richard Nixon (bowling alley, 1973): Nixon had a one-lane bowling alley built under the North Portico. It was privately funded by friends (including Charles Rebozo, Robert Abplanalp, and Walter Annenberg) at a cost of about $40,700. This replaced or supplemented an earlier Truman-era alley. No congressional appropriation was needed for this private addition.
fordlibrarymuseum.gov
Gerald Ford (outdoor swimming pool, 1975): Ford installed an outdoor pool on the South Lawn after Nixon converted the indoor pool into the Press Briefing Room. It was fully privately funded (around $52,000$67,000 via donations, with limits per donor) to avoid using taxpayer money during a time of inflation and budget concerns. Construction proceeded without federal funds or apparent direct congressional approval for the build.
whitehousehistory.org
Harry Truman (balcony and earlier bowling alley): Truman personally funded the Truman Balcony addition from his household account. He also received the first White House bowling alley in 1947 as a gift (installed in the West Wing basement). These were modest and did not require congressional votes.
opb.org
Other minor additions: Presidents like Dwight Eisenhower (putting green), Barack Obama (basketball court conversion), and others made recreational or decorative changes, often with private or existing resources. Franklin D. Roosevelt's indoor pool (1930s) was funded by public/private campaigns and small donations, not direct congressional action for that specific feature.