Final answer:
To avoid potential side effects, the client should limit their intake of coffee, cola, and chocolate while taking theophylline (Theo-24).
Step-by-step explanation:
When taking theophylline (Theo-24), it is important for the client to limit their intake of coffee, cola, and chocolate. These items contain caffeine, which is a methylxanthine, like theophylline. Both theophylline and caffeine have stimulating effects on the central nervous system, so consuming them together can potentially lead to increased side effects such as nervousness and restlessness.