When you push yourself, it's not uncommon to be out of gas towards the end of your workout. But that's the point where you need to push harder. To surpass your limits and become better the next time you train. However, without fuel, it's going to be hard to do so.
For this reason, there are a number of endurance products available. Either to act as fuel for the body, or to enable it to keep going well past your usual limits. Supplements like antioxidants, electrolytes, ketones and more could be just the thing you need to push your workout further.