No, if a food item had no water molecules in it, it would not heat up in the microwave. Microwave ovens work by emitting electromagnetic waves, specifically microwaves, which interact with water molecules in the food. These microwaves cause the water molecules to vibrate and generate heat, which then cooks the food from the inside out.
If there are no water molecules present in the food, there would be nothing for the microwaves to interact with, and therefore, the food would not heat up. The absence of water molecules means that there is no medium for the microwaves to transfer their energy to, and as a result, the food would remain cold even after extended exposure to the microwave radiation.
It's worth noting that different microwaveable food items contain varying amounts of water, and this impacts how they heat up in the microwave. Foods with higher water content tend to heat up more quickly and evenly in the microwave compared to those with lower water content.