A few days soak in a tub/tote with (initially warm) water and a powdered (clothes) washing detergent, such as Surf. But pretty much any detergent will do.
Some will float off within a day, most after 2 or 3 days. Those that are stubborn, either toss, or let soak a few more days.
Use a stiff hand brush to remove any remaining film of clinging glue or residue. Use a bottle brush on the inside.
Rinse inside and outside well (e.g., Jet Spray washer on faucet) with hot water. Inspect inside and outside thoroughly.
Then sanitize (Starsan) and they're ready to fill.
I always save my own previously cleaned bottles as much as possible. I know their whereabouts and when rinsed out and/or soaked right after pouring out, it saves time on the next cleaning.