First let us understand how our brain functions. Our sensory organs receive sensory information from the brain and the body acts on these messages. Once your brain becomes accustomed to a constant signal, it tends to ignore it, and focuses on looking for more pronounced changes. This is the reason why we don’t find our tea or coffee sweet once we have it after eating something relatively sweeter.
If you’re constantly tasting sweet, sweet things become the norm, and your brain doesn’t notice the difference. However, if you do something completely opposite, like eating an orange, your brain will signal that as “extra sour” due to the sudden change. Your brain returns to “normal” after you let your senses rest a bit.
When you eat a lot of sweets, your taste buds get used to that amount of sweetness. This is called sensory fatigue and happens with not just your taste buds but all of your senses. They get used to an environment if they are exposed to it for a long time.
What’s happening here is calibration. Your senses are calibrated to a continuous condition. After this, it only senses relatively.