Just bought some '100% maple syrup' locally, but it's VERY clear that it is not. Must be diluted with water as it is extremely non-viscous. Tastes sugary as well.
I've been sugaring for about 7 years now and am somewhat knowledgedable in this area. I would point out that there are severe fines for "adulterating" maple syrup in VT, as well as in the other New England states. Although aldulteration is very uncommon, some people do still try to get away with it, and they
always get caught. The most commonly attempted method is adding cane sugar to reduce the amount of sap and energy inputs needed to produce the syrup. Watered down syrup is less commonly tried, because if syrup does not have a high enough density, it spoils very quickly. For this reason, maple syrup can only be legally offered for sale if it has a density of at least 66% sugar by weight. This works out to a little over 11 pounds per gallon. Sugarmakers use a unit of density called "Brix" to measure the syrup density.
While all pure maple syrup has the same density (between 66-67 Brix), syrup
viscosity can vary somewhat, and the sugarmaker has virtually no control over it. (Yes, density and viscosity are two different, but generally related things). In general, the lighter grades of syrup, typically made in the early part of the season, tend to be less viscous then the darker grades, even though they all have the same density, by law. Grade A Light, (called "Fancy Grade" in VT) is the lightest grade, and tends to have only a very slight maple flavor. It also tends to be less viscous then the darker grades. Syrup newbies who are used to Mrs. Butterworth might think its been "watered" down. To complicate things even more, temperature has a profound effect. Syrup thins out very quickly as it is warmed, relative to syrup straight out of your refrigerator.
If I had to guess, I'd say you had some warm (i.e. room temperature) Grade A Light, with a particularly delicate/subtle maple flavor. If you think otherwise, you should contact your state's Department of Agriculture and report the suspected adulteration. They can run certain tests to check the purity of the syrup, since such nefarious activity gives all sugarmakers a bad name.
Happy Sugaring!