Did you ever see someone eating or drinking while wearing headgear?

I've never seen anyone eating.
Drinking yes.

I used to wear a cervical headgear when I was younger, but I never had any meal with it

Drinking is often done, mostly using a straw or something because drinking from a glass is not that easy with a facebow protuding from your face.

Eating is absolutely possible but not very practical because all kind of stuff gets stuck between your teeth and the facebow, that's why you don't see it.

(Of course if someone wears a headgear-activator combination both eating and drinking are practically impossible )

I had my headgear wired in (yes...it actually does happen) for 18 months and i managed everything as normal...it's not as hard as it seems...It hurts like hell though...I had High-Pull with a cervical neck strap but it went too far and i ended up with Reverse-Pull headgear which is like really hard to eat with!!!

I saw a boy drinking water in the Santiago's Way with headgear (cervical) and activator. He had some troubles to did that

I wear my headgear with my modified twinblock from the shop and I always drink water with my headgear in.
If you practice a bit you can manage it without spilling too much.
Eating yoghurt or soft ice is also no problem.
Chewing is impossible with plastic covered teeth from the twinblock.

Is that hard or awkward or difficult to eat with it on?

I once saw a child with a face mask in a pizzeria, his mother asked if he could eat with the appliance on, and they said doubtfully yes, unfortunately I had to go at that time