If you’re coming from Cusco, consider
bringing along an oxygen bottle. These small bottles of oxygen are sold to
travelers visiting Machu Picchu, which is almost 2,000 meters lower than the
highest point in the Uyuni tours, but are harder to find in Bolivia. They wont
last you the whole trip but most people who get altitude sickness start
adjusting to the altitude and feeling better within a day or two.
Take it Easy