Nothing.
The Suzuki Sierra is a great little city runner.
We never took it onto the beach, but I hear it's ideal for that sort of four-wheeling activity.
It is the common knowledge that they tip over on steep inclines. If you do go off-roading, be wary of this... they have a short wheel base.
My wife and I found this car a good, reliable no-frills car.
The only thing it lacked was power and speed. Overtaking can be a stressful (and potentially dangerous) pastime, as the top speed it goes comfortably is about 100km/h. Any faster and the engine sounds like it's working a little too hard. Noise inside the cabin is a little loud at these speeds, too. Forget about listening to the radio on the freeway (unless you have a booming sound system).
Even during city driving, I found that I had my foot down on the floor very often. A long incline made it very difficult to stay at 60 or 70km/h. Cars are continually overtaking you.
But if you don't take on the highways, and you want a reliable, small city car that runs on the smell of an oily rag, the Sierra is perfect.
The Suzuki Sierras do have go. Depends on what year and model really. My mate has an '84 model and it goes past 140km/h.