What's the deal with pumping in sugar water ?

Not a clue. First time I have heard of it. Why don’t you ask the guys at Newart?

Osmotic Apparatus
The movement of the substances involved in osmosis is shown in the illustration Principle of Osmosis. Between the two halves of the you-shaped tube is a semipermeable membrane, such as a piece of animal bladder, parchment, or cellophane. Arm A contains a solution of sugar and water and arm B contains pure water. The water molecules on both sides of the membrane hit the membrane and pass through. (The membrane is permeable to water.) The sugar molecules also hit the membrane, but, because of the composition of the membrane, only a few (the ones traveling at very high speeds) pass through. (The membrane is impermeable to sugar.)

More water molecules touch the membrane on the side in contact with the pure water (side B) than on the side in contact with both sugar and water (side A). More water moves from side B, the pure-water side, to side A than from side A to side B. This net movement of water through the semipermeable membrane into the sugar-and-water solution constitutes osmosis.

As water moves into the solution, the volume of the solution (illustration 2, side A) increases. The increased volume eventually builds up so much pressure that the force of the pressure causes as much water to leave the solution (side A) as enters. This pressure, called osmotic pressure, causes the flow of water to be equal in both directions.

Effect of Sugar
Plants’ cell walls become swollen and rigid when the cells fill with water. In other words, the cells become turgid, or swollen and hard, when osmotic pressure builds in the cells. This action keeps the leaves of the plant from wilting and allows it to stand up in sunlight, biology teacher Nigel D. Purchon writes on his websute. Purchon adds that when a concentrated sugar solution is added, the cell walls shrink and pull apart from each other —- and the plant wilts. Sugar lowers the osmotic potential of the water present in the soil, making less water available for the plant to take in from the soil.
Effect of Salt
Plants require some mineral salts for survival. Salt water in high concentration, however, dehydrates the plant. A high salt-solute concentration in the soil pulls water away from the plant cells, through osmosis, and deposits it into the soil. The Salinity Management Guide website reports that different plant species have differing tolerances for soil salt levels. Injury to the plant occurs when tolerance levels are reached or exceeded.

Come on guys a lot of serious pumpers have tried this and say it makes a difference, I’m interested as to why ?

The guys who said it made a difference were also guys that had spent 4 hours in the pump! That much pumping is going to make you huge no matter what you are pumping in.

Huge as in ‘hugely swollen with lymphatic fluid.’