Overconsumption of sugar-sweetened beverages (SSBs) can lead to dental caries and obesity. One alternative is to switch from SSBs to their diet counterparts. However, our rat data suggested that this switch may not be readily accepted; in a previous study intakes of saccharin solutions were unexpectedly low in rats that had prior access to sucrose solutions. To discover why this happened, we ran experiments containing two stages: Stage 1, 12-day exposure to palatable solutions or water; Stage 2, 12-day access to saccharin. In Experiment 1 rats given access to either 10% sucrose or 10% glucose in Stage 1, when switched in Stage 2 to saccharin showed both a successive negative contrast (SNC) effect and reduced saccharin acceptance throughout this stage. In final tests, the Water group displayed a greater preference for the saccharin solution over 2% sucrose than the other two groups. Experiment 2 used maltodextrin solutions to test whether this SNC depends on the palatability or the energy context of the initial solution. The results indicated that palatability (liking) is the most important factor. SNC is normally transient; we will discuss why the present effect is unusually persistent. This effect may be a factor in rejection of diet drinks.