Manipulating your swing speed in the sand is a common, deadly mistake. The results are rarely good… and no surprise, I mean… you’re trying to be consistent without using a consistent swing. By accelerating gradually until impact your swing is under control, consistent and efficient. Not to mention, you avoid the number one fault of poor bunker players, which is deceleration.
Never, ever swing faster or slower than normal in attempts to hit the ball different distances. The best ways to change your swing speed are by choosing a more suitable club, choking down if necessary or by shortening the length of your backswing period.