The bus in question is not unlike this one, only with more pizza boxes
Despite being gross to deal with, these are the best-case kinds of messes. Most of the time, sweeping away crackers or half eaten bagels and avoiding seats with smears of (what I hope is) ketchup or cream cheese is usually pretty simple. It's the food-related messes that you don't see that are cause for alarm.
One time, I witnessed a man eating from a large bag of chips while standing on the 95. They must have been so delicious that, after a couple of handfuls, he would lick his hand of the simulated ketchup flavour. As the bus braked sharply, he took his sticky, saliva-loaded hand and grabbed the pole for support! Once the bus was fully stopped, he took that same hand and fished out another handful of chips from his bag. This cycle (hand licking included) repeated until he disembarked, leaving me — and I'm sure anyone else that was hypnotized by his egregious display — thoroughly disgusted. If I were the Adrian Monk-type, I would definitely go and disinfect that pole, or flat out replace it, but instead I just made sure not to touch it. Doesn't do much for the next guy, though...
Gum is terribly disgusting, but at least you can see it