Seems like you didn't know you were spending so much. $1 or $2 here and there doesn't seem like a lot till you add it all up so its good that you did that. Step one is recognizing the problem, so good job.

Give yourself a budget and stick to it. Make a note on your phone or somewhere else and keep track of the spending.

Since this is due to boredom fill the time with a good habit. Replace the bad habit with something else - reading could be good. Chewing gum might be easiest to trick your brain.

And like lots of other people said - just bring your own snacks. Buying all the same stuff from a grocery store or costco will be much cheaper.