Can i drink alcohol (500ml - 1l) if i am on doxy + cipro (ciprofloxacin) or is it not recommended? (i am on my 3rd day treatment)

Ethanol: It is usually recommended not to take ethanol with antibiotics. Now, different to the popular belief that it directly affects abx efficacy it is more so to the decrease in quality sleep and recovery. In summary, no biggy if done with moderation and if it is not something like Metronidazole. Ciprofloxacin and Doxy should be fine.

Ethanol and abx: Drinking 500 to 1000 ml is way too much. Sipping 1 oz of wine as a toast or to honor a person is ok and sufficient. Please avoid hard liquor, beer, and mixed drinks.

No: I am not sure you are being serious in asking whether drinking 1/2 liter to a full liter a day of some kind of distilled sprits is "recommended?" It isn't recommended for ANYBODY, let alone someone being treated for an infection. Since you are on 2 antibiotics, I will assume its a serious infection. Alcohol impairs our immune system and healing. This is a dangerous amount of alcohol. Stop now.

Wait 48 hours: There has been little research conducted on this subject. However, the advice given by many of the manufacturers is that you should avoid drinking alcohol while taking antibiotics and for 48 hours after finishing the course of the treatment. Remember: moderation is the key.