Another page of the FF7 Remake game guide describes The Party Never Stops side quest from Chapter 9-the Town that Never Sleeps.
Meet the dealer, then follow Johnny to the bar and talk to the clothing store owner. Now go to Materia Vendor and talk to him. Go with Johnny to the hotel and use the special Vending Machine. Depending on what level of assess you have, you can get better rewards. Go back to the dealer and give him "The Sauce."
Now go to the restaurant and talk to the owner. You can advise him by choosing the Stove, Fridge or Power Supply option - choose the one that suits your ultimate purpose. Then follow Johnny, who will feel unwell after eating, and talk to him. Go to the apothecary and you have to find the sick (how many depends on the level and whether you own the cleansing matter). You'll find the sick one in the restroom, in the restaurant.
Go back to your pharmacist and you'll get a Vip Card. Follow her to the owner of the Clothing Store, and after more dialogues, you will complete the side mission.
Reward: Turbo Ether and access to the last side mission in Chapter 9.