Tinder is great app for hookups mainly due to the sheer number of users that are on it (a respectable 57 million as of 2019). Finding a willing hookup buddy in your area is undoubtedly a numbers game, and while not everyone on this app is on it for a casual fling, the odds are high that you'll be able to connect with users that are looking for something casual tonight. Not to mention, it's beyond easy to use. Create a profile with some photos, choose an age and location range for the person you're looking for, and start swiping (left to reject, right to accept). If you both dig each other, you'll be able to send messages to get things started.
If you don't have the patience to weed out matches that are explicitly looking for a no strings attached hookup, a quick search on FriendFinder-X will probably make you pretty happy. You can search for potential matches using filters that range from proximity, sexual preferences and even cup size. Too lazy to search? The app has a list of compatible profiles sent to you for your consideration.