After 47 years with Type 1 I've learned a few things.
First is that most people haven't a clue about diabetes--even many who have the disease.
Second is that you can't miss giving sugar or Pepsi or hard candy. Not chocolate: the fat slows down sugar absorption.
If glucose is already high, a Pepsi isn't going to matter. If it's low, Pepsi etc will be just what the doctor ordered.
Look for weird behavior: angry and short, can't concentrate, incoherent (worse than usual!) acting "drunk" ---all are some symptoms.
+1 on give it even if I say I'm fine. My wife can tell you stories about the things I've done when glucose was low that I cannot remember doing or saying.
There are a lot of diabetics out there and even more ignorance. Do some reading. Your friend with diabetes will appreciate it.
Vocatus atque non vocatus, Deus aderit.