Uhhu ,
Welcome to Bike Forums.
Not knowing your abilities it's tough to recommend a ride and not knowing what you define as "Epic" makes it tougher.

If somebody was visiting San Francisco and looking for bragging rights........

San Francisco, out across the Golden Gate Bridge.
Then ontinue into Tiburon for breakfast on the deck outside at Sam's,
Next catch the ferry to Angel Island and bike around the entire island.
Return ferry to either Tiburon and back across the bridge. or if you've biked enough for the day, ferry to San Francisco.

Make reservations for the Ferry (s) and ideally Sam's (or plan to be there early)

This wont get you bragging rights for bicycle prowess, but you sure can name drop when you get home.

Barry