A sleeper cab hardly has enough space for full-size gym equipment. Even a small set of weights and a folding exercise bike can quickly take up most of your sleeping space. Fortunately, there are lightweight, compact, and effective exercise equipment options that are ideal for a driver.
First, a simple pair of running shoes and workout clothes appropriate for the weather are great places to start. These simple items will allow you to take walks and start jogging, and they will make sure your work/driving clothes stay clean.
Second, consider lightweight equipment like resistance bands and a yoga mat. The mat will make stretching and static exercise more comfortable, and the resistance bands can allow you to do strength training without lugging around weights.