How does the sperm get through the layer of the eggs to cause fermentation?

Answer 1

It's quite a complicated process you should look at wikipedia but basically

Where the spermatozoon is about to pierce, the yolk (ooplasm) is drawn out into a conical elevation, termed the cone of attraction. Once the spermatozoon has entered, the peripheral portion of the yolk changes into a membrane, the vitelline membrane, which prevents the passage of additional spermatozoa

Also fertilization occurs not fermentation that's a completely different process

Answer 2

Sperm does not cause fermentation in eggs. Sperm fertilizes an egg by penetrating the outer layer of the egg, called the zona pellucida, and merging with the egg's nucleus. This process initiates fertilization, leading to the formation of an embryo. Fermentation, on the other hand, is a metabolic process that typically involves the breakdown of sugars by microorganisms, such as yeast or bacteria, to produce energy.