Sarah
My sick day 'rules' for ketones say that if  BG is below 8.3mmol/l . To check  ketones  every 2 hours and if present to take insulin  (specified amounts  depending on the ketone level) and  to drink a glass of a sugary drink  or fruit juice 
You use relatively large amounts of insulin to get rid of ketones and the danger of taking insulin and no glucose at this level is a hypo. Your body also needs some fuel to function properly in fighting any infection.
 (flat coke is suggesting  if you are  vomiting . They also say to call doctor if  you have ketones and vomiting persists ... even if glucose levels aren't high)
Above 8.3mmol/l  my 'rules'  say to drink  water, plus of course the necessary insulin (other diabetics on the course suggested Evian water for the bicarb, the doctors seemed to agree with that)  
 
You need to get a set of rules, especially for you, for if you are sick and have ketones again. Have them written out so you can refer to them (easier than trying to remember when you feel ill)  You need a lot more insulin when you have ketones than normally but you really need individual guidance as to how much and when.