The alphabite is the best bite of a meal or snack. The meal or snack is usually composed of numerous different ingredients and textures, allowing for variability in taste from one mouthful to the next. Thus, some bites are better than others and there is a particular mouthful that is superior to the rest. This superior mouthful is known as the 'alphabite.'
When eating a sandwich with crust, for instance, the alphabite could be considered the middle portion of the sandwich where you get to eat 100% meat/cheese/softbread/dressings. No crust. Thus, the 'alphabite.'
The 'alphabite' of a cookie may be the place on the cookie where multiple chocolate chips have gathered, thus giving you a high chocolate-to-dough ratio in that area of the cookie, leading to the 'alphabite', or best bite of that particular cookie.
The place on a slice of pizza where three pepperoni got stuck together resting atop an entire sundried tomato would be the location of an 'alphabite.' and so on...