Always be ready and well equipped with the essential accessories to have in your tennis bag. We exclude here the equipment necessary to play (racket, shoe) as well as the clothes.
Balls are obviously part of the strict requirements for playing tennis, so it is important to arrive with one or more tubes. It's always best to have extra new balls, which allow you to have spare balls to replace those that are flat or can get lost while playing outside. Make sure you have balls that are suitable for the playing surface (hard vs. clay).
Overgrips are very useful mainly to add superior grip, better sweat absorption or to extend the life of the base grip. While it is best to have an overgrip on before the game or practice, it is sometimes necessary to change them during the session (as we often see the pros do during breaks in play), whether it is to replace a worn out overgrip or to get a dry one during a wet session. A small pair of scissors can also be useful for finishing the grip.
On hot days or during intense sessions, sweat is bound to be present. There is nothing more unpleasant than to be soaked, to have it drip into your eyes or to make your hands slippery. It is therefore important to have a towel in your bag to dry as much as possible during breaks and after the session. You can also include a shower towel for those who have access to them in clubs or training centers.
A simple and often forgotten item at home, carrying a water bottle is especially important when playing on outdoor courts where access to water is not necessarily close or even accessible. It is obviously essential to stay hydrated during and after a sports session.
Like the towel, wristbands are a useful tool for staying as dry as possible on the court between points. For those who sweat more generously, there are double wristbands that cover more surface area and absorb more moisture. Headbands and caps serve the same purpose, primarily to keep sweat out of the eyes, and in the case of caps or visors, to provide shade from the sun.
Dressings / Bandages
Playing tennis comes with some risk of injury, with varying degrees of severity, but most injuries or discomforts can be treated on the spot. For example, scratches and blisters are among the common cases seen on the courts, so have some bandages to use as needed. Having a bag or two of emergency ice is also helpful for falls.