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.
Be yourself. Everyone else is already taken.
Vocatus atque non vocatus, Deus aderit.