Try adding a couple drops of extracts, like cinnamon or vanilla or orange to a pitcher of water. After your water is scented (or flavored, as suggested below), take a deep breath through your nose, inhaling the scent, before drinking. Your sense of smell has everything to do with your sense of taste.
Try an infusion pitcher. Several brands and styles available. Lets you infuse fruit taste into water without adding any pulp or other solids. You can use fresh or frozen fruit; citrus, berries, herbs, peppermint, chocolate mint (!), etc. If you want it sweeter, stevia is a natural substance and shouldn't give you headaches.
Do you have a favorite flavor? Or a favorite scent or perfume? You might start there as a guide.
If you try it, let us know how you make out. If you find something else to help, please let us know that, too!