Do you have any CPU limits set on the VM?
Is the sqlservr.exe process actually using all of the guest CPU on the SQL Server VM (as shown in Windows Task Manager or Resource Monitor), or is it another process, or is it "System"? If it is the System process, you could be encountering latency in the kernel (for example, long wait times accessing your system's vmdk file due to storage latency), which would require further troubleshooting.
If it's the SQL Server process, you probably just need to allocate more vCPU to the machine. If you're running ESXi 5.x or higher, you add multi core vCPUs, which would get you around the 4 CPU constraint found in Windows Standard Edition. If you really want to know exacly "what" vCenter is doing with SQL Server to cause the spikes in CPU, Activity Monitor in SQL Server Management Studio could tell you the biggest consumers of CPU within SQL Server.