The reaction used to produce sugar in plants is Photosynthesis,
6CO₂ + 6H₂O + heat ⇆ C₆H₁₂O₆ + 6O₂↑
we can see that this reaction is endothermic, it absorbs heat to occur
If we were to add more heat or increase the temperature, the left side of the equilibrium will be able to react much more, which would produce more glucose (aka sugar)
Hence increasing the temperature will shift the equilibrium to the right or towards the Products