Can i get an std by sharing a cigarette?

No: Stds are not spread by that small of amount of saliva on an inanimate object like a cigarette. They are spread by infectedbody secretions but saliva has far too small a volume to spread stds.

NO: Generally speaking, no. But if the person you share cigarette has cold blisters on his/her lips or anywhere in the mouth, (herpes infection (type1), you can get herpes from the person.