I use lucozade or glucose tabs even at 3.5. Anything else sugary can make my tum go washing-machine -like and can make me feel like vomiting. Not every time but enough to want to avoid it.
Depends how low really but nothing specific. Jelly babies, regular coke, orange juice, lucozade, they all work. Whatever is available at the time I guess. I would have to be very low and feeling shaky for this though. Otherwise, I would just have an apple or cereal bar or something.
Liquid glucose (Lucozade and Coke etc) by far works the fastest, for a 3.5 I would use 2 jelly babies followed by a small carby snack if it was within 3 hours of injecting.
My rule is that if I'm in the 3s then it's a mild hypo so have 3-5 dextro tablets. If I'm in the 2s then if things could get hairy if I drop any further as if my levels are in the 1s then I could lose consciousness so i'll get some lucozade down me asap.