out = [
    ["FizzBuzz", "Fizz", "Fizz", "Fizz", "Fizz"],
    ["Buzz"],
    ["Buzz"]
  ]
  (1..100).each do | ii |
    puts out[ii % 3][ii % 5] || ii
  end

Thanks!

PS: i am assuming this is the fastest you can do in ruby (but I suspect that blocks are expensive alas)

PS2: passing the test is interesting, having a look at the good and/or best answers would be a decent award for having tried in the first time.