What is a cheat to make sims best friends in The Sims 3?

Hold down Control, Shift, and C.

A little blue-ish box will appear at the top of your screen.

Type in " testingcheatsenabled true " (without the quotes).

Now click on the "Relationships" button.

Go to the Sim you want your Sim to become best friends.

Drag the bar (The little thing under a Sims picture) all the way up.

Your Sim now has a new best friend!