- quart of cider
- sulfuric acid
- oranges and lemons
- spicy paste and barley water
By the time they ran out of lemons, six days the two sailors in group 5 showed remarkable improvement. No other group showed any improvement. I guess with an N of 2 you better hope for an NNT of 1.
Read the wikipedia page, it has a fascinating account of how this medical breakthrough was ignored and missed for 47 years until lemon juice was issued as part of provisions in 1794.