
Training kit
A gym bottle should fit the bag, open when you need it and be straightforward to clean. Capacity is only one part of the purchase.

Measure the pocket or compartment where you intend to carry it. A large bottle may fit vertically but prevent the bag closing, while a narrow bottle may slide out of a loose side pocket. Check the filled weight as well as the empty dimensions, especially if you walk to training.
Look at the lid and locking mechanism. You should be able to tell when it is fully closed. A flip spout can be convenient, but accidental pressure in a bag may open it unless the design prevents that. Keep electronics separately protected rather than trusting a new bottle without checking it.
A wide mouth can make cleaning easier, while a narrow drinking opening may feel more convenient during a pause. Some lids contain seals, valves or straws that need removal for cleaning. Read the instructions and make sure you can reach the parts where moisture remains.
Check whether replacement seals or lids are available. A bottle that remains sound but has an unavailable worn seal may become frustrating to use. Follow temperature and dishwasher limits rather than assuming metal, plastic or glass all behave the same way. Do not put hot liquid in a bottle unless it is designed for it.
Think about session length, the journey and access to a reliable refill point. A smaller bottle with a known refill option may be easier to carry than a very large one. Do not assume a fountain or café will be open, especially for an early or outdoor session.
Individual fluid needs differ with conditions and health circumstances, so a bottle size is not a drinking prescription. If you have been given medical advice about fluid intake, follow it. Keep the bottle accessible during appropriate breaks rather than placing it where you need to cross other people's equipment.
Empty, clean and dry the bottle according to its instructions after use. Leaving it sealed in a gym bag is not a storage routine. Choose a design whose cleaning process you are willing to repeat; an elaborate lid is only useful if you can maintain it properly.