I've got two solutions this go-round.  First, the solution I would present were I asked to do this in an actual job interview:

  for n in 1..100
    mult_3 = ( n % 3 ).zero?
    mult_5 = ( n % 5 ).zero?
    if mult_3 or mult_5
      print "Fizz" if mult_3
      print "Buzz" if mult_5
    else
      print n
    end
    puts
  end

-mental