Has anyone ever taken their own snacks into the cinema?

A couple of times.

I still get the popcorn pretty often, though the price is pretty ridiculous. I don't know what toxic gunk they use to flavor it, but its the best popcorn.

Always bring a bottle of water. I'm not gonna be that guy who gets a coughing fit in the middle of the movie. But i've smuggled just about everything into the movies back in the day. Used to wear a trench coat I would stick bottles of boones in with a subway sub. Haha. But now that i'm all grown up, I find I can get through a two hour movie just fine without stuffing my face.

i have taken an entire mcdonald meal into the movies

I thought everyone did.

Frequently
A big coat is the key to smuggling cheap snacks👍

I've taken Wendy's to the cinema with my siblings back in 2003, when we saw Terminator 3.

I always do. Cheaper than the candybar.

I stop at the supermarket and get some popcorn and a chocolate bar.

Yes, I've brought snacks and several times have taken a flask in with some liquor or other.
The last time I did the flask thing was at 28 Days Later...so it has been a good while and I no longer even drink.
I still feel bad..We were so annoying..We got ripped.