If you are seeing long code strings in your Event Description, it is likely to be a result of HTML in your calendar events, which isn't automatically recognised by Salesforce, like it is by Google.
To be able to clearly see the HTML Descriptions from your Google Calendar sync events you need to create a small Visualforce Page which renders the text of the Description box without the code.
You need to be a Salesforce Administrator to be able to do this.
Create a Visualforce Page in Salesforce
1. Click the Gear icon and click Setup
2. Type 'visualforce' into the Quick Find box and click Visualforce Pages.
3. Click New.
4. Give the page a Label and Name, we suggest: Event Description HTLML (Read only).
5. In the Visualforce Markup box paste in the following code:
<apex:page standardController="Event">
<apex:outputText value="{!event.description}" escape="false" />
</apex:page>
6. Click Save.
7. Now add this field to your Event Page Layout.