There’s a load of factors that will affect sales
Day games are better than night games because you can sell through the eighth inning as opposed to just the seventh. A rivalry game will boost sales -- a Padres game in May, not so much. For weather, you don't want it too cold or hot outside and rain expectedly ruins everything. Vendors are aware if the starting pitcher is a fast worker, like when Mark Buehrle was on the mound for the White Sox, or more methodical. Pitching changes are a blessing.
Winning is the most important factor
... in maintaining the proper flow of booze (in baseball standings too, I guess). It's tricky, but an ideal situation is that the Cubs score a batch of runs early in the game, not so many that it's a blowout and fans leave but enough to keep everyone engaged and sticking around for that extra beer or two.